Continuously variable transmission

ABSTRACT

Inventions are directed to components, subassemblies, systems, and/or methods for continuously variable transmissions (CVT). In one aspect, a control system is adapted to facilitate a change in the ratio of a CVT. A control system includes a control reference nut coupled to a feedback cam and operably coupled to a skew cam. In some cases, the skew cam is configured to interact with carrier plates of a CVT. Various inventive feedback cams and skew cams can be used to facilitate shifting the ratio of a CVT. In some transmissions described, the planet subassemblies include legs configured to cooperate with the carrier plates. In some cases, a neutralizer assembly is operably coupled to the carrier plates. A shift cam and a traction sun are adapted to cooperate with other components of the CVT to support operation and/or functionality of the CVT. Among other things, shift control interfaces for a CVT are described.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of, and hereby incorporates byreference in its entirety, U.S. Provisional Patent Application60/948,152, filed on Jul. 5, 2007.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The field of the invention relates generally to transmissions, and moreparticularly to methods, assemblies, and components for continuouslyvariable transmissions (CVTs).

2. Description of the Related Art

There are well-known ways to achieve continuously variable ratios ofinput speed to output speed. Typically, a mechanism for adjusting thespeed ratio of an output speed to an input speed in a CVT is known as avariator. In a belt-type CVT, the variator consists of two adjustablepulleys coupled by a belt. The variator in a single cavity toroidal-typeCVT usually has two partially toroidal transmission discs rotating abouta shaft and two or more disc-shaped power rollers rotating on respectiveaxes that are perpendicular to the shaft and clamped between the inputand output transmission discs. It is generally necessary to have acontrol system for the variator so that the desired speed ratio can beachieved in operation.

Embodiments of the variator disclosed herein include spherical-typevariators utilizing spherical speed adjusters (also known as poweradjusters, balls, planets, sphere gears or rollers) that each has atiltable axis of rotation adapted to be adjusted to achieve a desiredratio of output speed to input speed during operation. The speedadjusters are angularly distributed in a plane perpendicular to alongitudinal axis of a CVT. The speed adjusters are contacted on oneside by an input disc and on the other side by an output disc, one orboth of which apply a clamping contact force to the rollers fortransmission of torque. The input disc applies input torque at an inputrotational speed to the speed adjusters. As the speed adjusters rotateabout their own axes, the speed adjusters transmit the torque to theoutput disc. The output speed to input speed ratio is a function of theradii of the contact points of the input and output discs to the axes ofthe speed adjusters. Tilting the axes of the speed adjusters withrespect to the axis of the variator adjusts the speed ratio.

There is a continuing need in the industry for variators and controlsystems therefor that provide improved performance and operationalcontrol. Embodiments of the systems and methods disclosed here addresssaid need.

SUMMARY OF THE INVENTION

The systems and methods herein described have several features, nosingle one of which is solely responsible for its desirable attributes.Without limiting the scope as expressed by the claims that follow, itsmore prominent features will now be discussed briefly. After consideringthis discussion, and particularly after reading the section entitled“Detailed Description of Certain Inventive Embodiments” one willunderstand how the features of the system and methods provide severaladvantages over traditional systems and methods.

One aspect of the invention relates to a method of controlling atransmission having a group of traction planets. The method includes thesteps of providing each traction planet with a planet axle and impartinga skew angle to each planet axle. In one embodiment, the method can alsoinclude the step of tilting each planet axle.

Another aspect of the invention concerns a method of facilitatingcontrol of the speed ratio of a continuously variable transmission(CVT). The method can include the steps of providing a group of tractionplanets and providing each of the traction planets with a planet axle.Each traction planet can be configured to rotate about a respectiveplanet axle. In one embodiment, the method includes providing a firstcarrier plate configured to engage a first end of each of the planetaxles. The first carrier plate can be mounted along a longitudinal axisof the CVT. The method can include the step of providing a secondcarrier plate configured to engage a second end of each of the planetaxles. The second carrier plate can be mounted coaxially with the firstcarrier plate. The method can also include the step of arranging thefirst carrier plate relative to the second carrier plate such thatduring operation of the CVT the first carrier plate can be rotated,about the longitudinal axis, relative to the second carrier plate.

Yet another aspect of the invention concerns a transmission having a setof traction planets arranged angularly about a longitudinal axis of thetransmission. In one embodiment, the transmission has a set of planetaxles. Each planet axle can be operably coupled to each traction planet.Each planet axle can define a tiltable axis of rotation for eachtraction planet. Each planet axle can be configured for angulardisplacement in first and second planes. The transmission can have afirst carrier plate operably coupled to a first end of each planet axle.The first carrier plate can be mounted about the longitudinal axis. Thetransmission can also have a second carrier plate operably coupled to asecond end of each planet axle. The second carrier plate can be mountedabout the longitudinal axis. The first and second carrier plates areconfigured to rotate, about the longitudinal axis, relative to eachother.

One aspect of the invention concerns a control system for a continuouslyvariable transmission (CVT) having a set of traction planets withtiltable axes of rotation. The control system includes a controlreference source configured to provide a control reference indicative ofa desired operating condition of the CVT. In one embodiment, the controlsystem also includes a skew dynamics module operably coupled to thecontrol reference source. The skew dynamics module can be configured todetermine an adjustment in the tiltable axes of rotation based at leastin part on a skew angle value.

Another aspect of the invention concerns a method of controlling acontinuously variable transmission (CVT) having a group of tractionplanets. Each traction planet having a planet axle about which thetraction planet rotates. The method includes the steps of providing acontrol reference indicative of a desired operating condition of the CVTand determining a skew angle based at least in part on the desiredoperating condition of the CVT. In one embodiment, the method includesthe step of applying the skew angle to each of the planet axles.

Yet one more aspect of the invention addresses a method of controlling acontinuously variable transmission (CVT) having a group of tractionplanets with tiltable axes of rotation. The method includes the steps ofproviding a control reference indicative of a desired operatingcondition of the CVT and sensing a current operating condition of theCVT. In one embodiment, the method includes the step of comparing thedesired operating condition with the current operating condition therebygenerating a control error. The method also includes the step ofimparting a skew angle to each of the tiltable axes. The skew angle isbased at least in part on the control error.

In another aspect, the invention concerns a method of controlling acontinuously variable transmission (CVT) having a group of tractionplanets arranged angularly about a longitudinal axis of the CVT, eachtraction planet mounted on a planet axle that defines a tiltable axis ofrotation. The CVT can have a traction sun in contact with each of thetraction planets. The traction sun can be configured to translateaxially. The method includes the step of coupling the traction sun to asun position locker. The sun position locker can be configured to retainthe traction sun at an axial position. In one embodiment, the methodincludes the step of providing a skew angle coordinator that can beoperably coupled to the traction planets and to the traction sun. Theskew angle coordinator can be configured to adjust a tilt angle of theplanet axles.

Another aspect of the invention relates to a control system for atransmission having a traction sun and a set of traction planets eachhaving a tiltable axis of rotation. The control system has a controlreference source configured to provide a control reference indicative ofa desired operating condition of the transmission. In one embodiment,the control system has a feedback source configured to provide afeedback indicative of a current operating condition of thetransmission. The control system can have a sun position locker operablycoupled to the traction sun. The sun position locker can be configuredto selectively hold an axial position of the traction sun. The controlsystem can have a skew angle coordinator operably coupled to thetraction planets. The control system can also have a decision processmodule configured to compare the control reference to the feedback. Thedecision process module can be configured to generate a signal based atleast in part on the comparison. The signal is configured to be passedto the sun position locker and to the skew angle coordinator.

One aspect of the invention relates to a control system for atransmission having a traction sun and a group of traction planetsoperably coupled to a carrier plate and to the traction sun. The controlsystem includes a control reference nut mounted coaxially with alongitudinal axis of the CVT. In one embodiment, the control systemincludes a feedback cam operably coupled to the control reference nutand to the traction sun. The feedback cam can be positioned coaxiallywith the control reference nut. The carrier plate is positionedcoaxially with the feedback cam. The control system also includes a skewcam coupled to the feedback cam and to the carrier plate. The skew camcan be configured to rotate the carrier plate about the longitudinalaxis.

Another aspect of the invention concerns a method for controlling acontinuously variable transmission (CVT). The method includes the stepsof providing a skew-based control system and operably coupling aneutralizer assembly to the skew-based control system. The neutralizerassembly can be configured to balance a group axial forces that aregenerated in the CVT during operation.

Yet another aspect of the invention involves a method of controlling acontinuously variable transmission (CVT) having a traction sun and agroup of traction planets each having a tiltable axis of rotation. Themethod includes the step of sensing an axial force imparted on thetraction sun during operation of the CVT. In on embodiment, the methodalso includes the step of supplying a force of equal magnitude and ofopposite direction of the axial force. The force can be configured to beoperably applied to the traction sun.

One aspect of the invention concerns a neutralizer assembly for acontinuously variable transmission having a skew-based control system.The neutralizer assembly can have a first resistance member configuredto generate a force in a first axial direction. In one embodiment, theneutralizer assembly has a second resistance member configured togenerate a force in a second axial direction. The neutralizer assemblycan also have a translating resistance cap operably coupled to theskew-based control system. The translating resistance cap can beconfigured to separately engage each of the first and the secondresistance members.

Another aspect of the invention relates to a feedback cam for askew-based control system. The feedback cam has a generally elongatedcylindrical body having a first end and a second end. In one embodiment,the feedback cam has a bearing race located on the first end. Thefeedback cam can have a threaded portion located on the first end. Thefeedback cam can also have a splined portion located on the second end.

Yet one more aspect of the invention addresses a skew cam for acontinuously variable transmission (CVT) having a skew-based controlsystem. The skew cam has a generally elongated cylindrical body having afirst end and a second end. In one embodiment, the skew cam has a firstthreaded portion located in proximity to the first end. The skew cam canhave a second threaded portion located in proximity to the second end.The first threaded portion has a lead that is smaller than a lead of thesecond threaded portion.

In another aspect, the invention concerns a carrier plate for acontinuously variable transmission (CVT) having a skew-based controlsystem and a group of traction planets. The carrier plate includes agenerally cylindrical plate and a set of concave surfaces formed on aface of the cylindrical plate. The concave surfaces are adapted tooperably couple to each of the traction planets. In one embodiment, thecarrier plate includes a threaded central bore configured to operablycouple to the skew-based control system. The carrier plate can also havea reaction face coaxial with the central bore. The reaction face can beconfigured to operably couple to the skew-based control system.

Another aspect of the invention relates to a leg assembly for acontinuously variable transmission (CVT) having a skew-based controlsystem. The leg assembly includes a leg having an elongated body with afirst end and a second end. The leg has a first bore formed on the firstend and a second bore formed in proximity to the first end. The secondbore can have first and second clearance bores. The second bore can besubstantially perpendicular to the first bore. The leg assembly can alsoinclude a shift guide roller axle operably coupled to the second bore.The shift guide roller axle can be adapted to pivot in the second bore.

One aspect of the invention relates to a leg for a continuously variabletransmission (CVT) having a skew-based control system. The leg has anelongated body having a first end and a second end. In one embodiment,the leg has a first bore formed on the first end and a second boreformed in proximity to the first end. The second bore can have first andsecond clearance bores. The second bore can be substantiallyperpendicular to the first bore. The leg can also have a third clearancebore formed between the first and second clearance bores. The thirdclearance bore can be configured to provide a pivot location for a shiftguide roller axle of the CVT.

Another aspect of the invention concerns a transmission having alongitudinal axis. In one embodiment, the transmission includes atraction sun that is coaxial with the longitudinal axis. The tractionsun can be configured to translate axially. The transmission can havefirst and second carrier plates that are coaxial with the longitudinalaxis. The traction sun is positioned between the first and secondcarrier plates. The transmission can have a planetary gear set operablycoupled to a control reference input source. In one embodiment, thetransmission has a feedback cam operably coupled to the planetary gearset and to the traction sun. The transmission can have a skew camoperably coupled to the planetary gear set and to the first carrierplate. The transmission can also have first and second resistancemembers operably coupled to the skew cam. The first carrier isconfigured to be rotatable with respect to the second carrier plate.

Yet another aspect of the invention involves a control referenceassembly for a continuously variable transmission (CVT) having askew-based control system. The control reference assembly includes acontrol reference nut. The control reference assembly can include firstand second resistance members coupled to the control reference nut. Inone embodiment, the control reference assembly includes an intermediatereaction member coupled to the first and second resistance members. Theintermediate reaction member can be located coaxially with, and radiallyinward of, the control reference nut. A rotation of the controlreference nut in a first direction energizes the first resistancemember. A rotation of the control reference nut in a second directionenergizes the second resistance member.

One aspect of the invention concerns a control reference assembly for acontinuously variable transmission (CVT) having a skew-based controlsystem. The control reference assembly has a control reference nut. Thecontrol reference assembly can have first and second resistance memberscoupled to the control reference nut. In one embodiment, the controlreference assembly includes a pulley operably coupled to the controlreference nut. The control reference assembly can have first and secondcables each coupled to the control reference nut and to the pulley. Thecontrol reference assembly can also have a spring retention membercoupled to the pulley and to the first and second resistance members. Arotation of the control reference nut in a first direction unwinds thefirst cable from the pulley. A rotation of the control reference nut ina second direction unwinds the second cable from the pulley.

Another aspect of the invention relates to a transmission having acarrier plate mounted coaxial with a longitudinal axis of thetransmission. In one embodiment, the transmission includes a group oftraction planets arranged angularly about the longitudinal axis. Thetransmission can include a planet axle operably coupled to each tractionplanet. The planet axle defines a tiltable axis of rotation. Thetransmission can include a planet support trunnion coupled to arespective planet axle. The planet support trunnion can have aneccentric skew cam configured to couple to the carrier plate. Thetransmission can also include a sleeve coupled to each planet supporttrunnion. The sleeve can be configured to axially translate. The sleevecan be configured to rotate. A rotation of the sleeve imparts a skewangle to each of the planet axles.

Yet one more aspect of the invention addresses a torque governor for acontinuously variable transmission (CVT) having a set of tractionplanets with tiltable axes of rotation. The torque governor includes acarrier plate mounted coaxial with a longitudinal axis of the CVT. Inone embodiment, the torque governor includes a shift cam operablycoupled to the carrier plate. The shift cam can have a threadedextension. The torque governor includes a first reaction arm coupled tothe shift cam. The first reaction arm can be operably coupled to thecarrier plate. The first reaction arm is coaxial with the longitudinalaxis. The torque governor also includes a second reaction arm operablycoupled to the first reaction arm. The first and second reaction armsare configured to rotate the carrier plate during operation of the CVT.

In another aspect, the invention concerns a method of adjusting a speedratio of a continuously variable transmission (CVT) having a group oftraction planets configured angularly about a longitudinal axis of theCVT. Each traction planet is mounted on a planet axle that defines atiltable axis of rotation for a respective traction planet. The methodincludes the step of imparting a skew angle to each planet axle.

Another aspect of the invention relates to a method of adjusting a speedratio of a continuously variable transmission (CVT) having a group oftraction planet configured angularly about a longitudinal axis of theCVT. Each traction planet has a tiltable axis of rotation. The methodincludes the step of imparting a skew angle to each tiltable axis ofrotation.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1A is a schematic diagram of a ball planetary continuously variabletransmission (CVT) and certain relevant coordinate systems.

FIG. 1B is a diagram of certain relative-coordinate systems related to acoordinate system shown in FIG. 1A.

FIG. 1C is a schematic diagram of certain kinematic relationshipsbetween certain contacting components of the CVT of FIG. 1A.

FIG. 1D is a representative chart of traction coefficient versusrelative velocity for a typical traction fluid and rolling contactbetween CVT traction components.

FIG. 1E is a free body diagram of a traction planet of the CVT of FIG.1A.

FIG. 1F is a schematic diagram of a traction planet of the CVT of FIG.1A showing a skew angle.

FIG. 2 is a block diagram of an embodiment of a drive apparatusconfigured to use certain inventive embodiments of CVTs and skew controlsystems and methods therefor disclosed here.

FIG. 3 is a perspective view of certain components of a CVT configuredto employ a skew angle adjustment to cause a tilt in the axis ofrotation of traction planets.

FIG. 4 is a block diagram of an embodiment of a skew control system thatcan be used in, for example, the drive apparatus of FIG. 2.

FIG. 5A is a schematic diagram of another embodiment of a skew controlsystem that can be used with, for example, the drive apparatus of FIG.2.

FIG. 5B is a schematic diagram of yet another embodiment of a skewcontrol system that can be used with, for example, the drive apparatusof FIG. 2.

FIG. 5C is a schematic diagram of one more embodiment of a skew controlsystem that can be used with, for example, the drive apparatus of FIG.2.

FIG. 6 is a cross-sectional view of a CVT configured to employ a skewangle adjustment to facilitate an adjustment in the speed ratio of theCVT.

FIG. 7 is a partially sectioned and exploded, perspective view ofcertain components of the CVT of FIG. 6. For clarity of illustration,the CVT is shown in two pages; wherein a plane perpendicular to the mainaxis of the CVT and passing through the center of the traction planetdivides the CVT in two sections.

FIG. 8 is a partially sectioned and exploded, perspective view ofcertain components of the CVT of FIG. 6. FIG. 8 is the second section,of the CVT illustrated, that compliments the section shown in FIG. 7.

FIG. 9 is a perspective view of a planet-leg assembly that can be usedwith the CVT of FIG. 6.

FIG. 10 is a cross-sectional view of the planet-leg assembly of FIG. 9.

FIG. 11 is a Detail A view of the CVT of FIG. 6.

FIG. 12 is a Detail B view of the CVT of FIG. 6.

FIG. 13 is a perspective view of a main axle that can be used with theCVT of FIG. 6.

FIG. 14 is a cross-sectional view of the main axle of FIG. 13.

FIG. 15 is a perspective view of a feedback cam that can be used withthe CVT of FIG. 6.

FIG. 16 is a cross-sectional view of the feedback cam of FIG. 15.

FIG. 17 is perspective view of a skew cam that can be used with the CVTof FIG. 6.

FIG. 18 is a cross-sectional view of the skew cam of FIG. 17.

FIG. 19 is a perspective view of a carrier plate that can be used withthe CVT of FIG. 6.

FIG. 20 is a cross-sectional view of the carrier plate of FIG. 19.

FIG. 21 is a partially sectioned, perspective view of a shift cam thatcan be used with the CVT of FIG. 6.

FIG. 22 is a perspective view of a leg assembly that can be used withcertain embodiments of a CVT that uses skew control.

FIG. 23 is a cross-sectional view of certain components of the leg ofFIG. 22.

FIG. 24 is a cross-sectional view of another embodiment of a CVTconfigured to use adjustment of a skew angle to cause adjustment of anangle of rotation of the traction planets of the CVT.

FIG. 25 is a partially sectioned and exploded view of certain componentsof the CVT of FIG. 24.

FIG. 26 is a Detail C view of the CVT of FIG. 24.

FIG. 27 is a perspective view of a main axle that can be used with theCVT of FIG. 24.

FIG. 28 is a perspective view of a feedback cam that can be used withthe CVT of FIG. 24.

FIG. 29 is a cross-sectional view of the feedback cam of FIG. 28.

FIG. 30 is a cross-sectional view of a yet another embodiment of a CVTconfigured to use adjustment of a skew angle to cause an adjustment ofthe speed ratio.

FIG. 31 is partially sectioned and exploded view of certain componentsof the CVT of FIG. 30.

FIG. 32 is a Detail D view of the CVT of FIG. 30.

FIG. 33 is a perspective view of a feedback cam that can be used withthe CVT of FIG. 30.

FIG. 34 is a cross-sectional view of the feedback cam of FIG. 33.

FIG. 35 is a partially sectioned, perspective view of a shift cam thatcan be used with the CVT of FIG. 30.

FIG. 36 is a cross-sectional view of certain components of an embodimentof a CVT having a skew-based control system and a neutralizer assembly.

FIG. 37 is a cross-sectional view of certain components of anotherembodiment of a CVT having a skew-based control system and a neutralizerassembly.

FIG. 38 is a Detail E view of the CVT of FIG. 37.

FIG. 39 is a cross-sectional view of certain components of yet anotherembodiment of a CVT having a skew-based control system and a neutralizerassembly.

FIG. 40 is a Detail F view of the CVT of FIG. 39.

FIG. 41 is a cross-section view of one more embodiment of a CVT having askew-based control system and a neutralizer assembly.

FIG. 42 is a partially cross-sectioned, exploded view of a controlreference assembly that can be used with the CVT of FIG. 41.

FIG. 43 is a cross-sectional view of the control reference assembly ofFIG. 42.

FIG. 44 is a plan view of a control reference nut that can be used withthe control reference assembly of FIG. 43.

FIG. 45 is a cross-sectioned perspective view of an intermediatereaction member that can be used with the control reference assembly ofFIG. 43.

FIG. 46 is a partially cross-sectioned perspective view of the controlreference nut of FIG. 44.

FIG. 47 is a Detail G view of the CVT of FIG. 41.

FIG. 48 is a cross-sectional view of another embodiment of a CVT havinga skew-based control system.

FIG. 49 is a Detail H view of the CVT of FIG. 48.

FIG. 50 is a partially cross-sectioned exploded view of certaincomponents of the CVT of FIG. 48.

FIG. 51A is a plan view of certain components of an embodiment of a CVThaving an inventive skew-based control system.

FIG. 51B is another plan view of the CVT of FIG. 51A.

FIG. 52 is a cross-sectional view of the CVT of FIG. 51A.

FIG. 53A is a Detail I view of the CVT of FIG. 51A.

FIG. 53B is a Detail J view of the CVT of FIG. 51A.

FIG. 54 is an exploded perspective view of the CVT of FIG. 51A.

FIG. 55 is a perspective view of a sleeve that cam be used with the CVTof FIG. 51A.

FIG. 56 is a partially cross-sectioned, perspective view of a planetsupport trunnion that can be used with the CVT of FIG. 51A.

FIG. 57 is a plan view of a torque governor having certain inventivefeatures.

FIG. 58 is a cross-sectional view of the torque governor of FIG. 57.

DETAILED DESCRIPTION OF CERTAIN INVENTIVE EMBODIMENTS

The preferred embodiments will be described now with reference to theaccompanying figures, wherein like numerals refer to like elementsthroughout. The terminology used in the descriptions below is not to beinterpreted in any limited or restrictive manner simply because it isused in conjunction with detailed descriptions of certain specificembodiments of the invention. Furthermore, embodiments of the inventioncan include several novel features, no single one of which is solelyresponsible for its desirable attributes or which is essential topracticing the inventions described. Certain CVT embodiments describedhere are generally related to the type disclosed in U.S. Pat. Nos.6,241,636; 6,419,608; 6,689,012; 7,011,600; 7,166,052; U.S. patentapplication Ser. Nos. 11/243,484 and 11/543,311; and Patent CooperationTreaty patent application PCT/IB2006/054911 filed Dec. 18, 2006. Theentire disclosure of each of these patents and patent applications ishereby incorporated herein by reference.

As used here, the terms “operationally connected,” “operationallycoupled”, “operationally linked”, “operably connected”, “operablycoupled”, “operably linked,” and like terms, refer to a relationship(mechanical, linkage, coupling, etc.) between elements whereby operationof one element results in a corresponding, following, or simultaneousoperation or actuation of a second element. It is noted that in usingsaid terms to describe inventive embodiments, specific structures ormechanisms that link or couple the elements are typically described.However, unless otherwise specifically stated, when one of said terms isused, the term indicates that the actual linkage or coupling may take avariety of forms, which in certain instances will be readily apparent toa person of ordinary skill in the relevant technology.

For description purposes, the term “radial” is used here to indicate adirection or position that is perpendicular relative to a longitudinalaxis of a transmission or variator. The term “axial” as used here refersto a direction or position along an axis that is parallel to a main orlongitudinal axis of a transmission or variator. For clarity andconciseness, at times similar components labeled similarly (for example,control piston 582A and control piston 582B) will be referred tocollectively by a single label (for example, control pistons 582).

It should be noted that reference herein to “traction” does not excludeapplications where the dominant or exclusive mode of power transfer isthrough “friction.” Without attempting to establish a categoricaldifference between traction and friction drives here, generally thesemay be understood as different regimes of power transfer. Tractiondrives usually involve the transfer of power between two elements byshear forces in a thin fluid layer trapped between the elements. Thefluids used in these applications usually exhibit traction coefficientsgreater than conventional mineral oils. The traction coefficient (μ)represents the maximum available traction forces which would beavailable at the interfaces of the contacting components and is ameasure of the maximum available drive torque. Typically, frictiondrives generally relate to transferring power between two elements byfrictional forces between the elements. For the purposes of thisdisclosure, it should be understood that the CVTs described here mayoperate in both tractive and frictional applications. For example, inthe embodiment where a CVT is used for a bicycle application, the CVTcan operate at times as a friction drive and at other times as atraction drive, depending on the torque and speed conditions presentduring operation.

Embodiments of the invention disclosed here are related to the controlof a variator and/or a CVT using generally spherical planets each havinga tiltable axis of rotation that can be adjusted to achieve a desiredratio of input speed to output speed during operation. In someembodiments, adjustment of said axis of rotation involves angularmisalignment of the planet axis in one plane in order to achieve anangular adjustment of the planet axis in a second plane, therebyadjusting the speed ratio of the variator. The angular misalignment inthe first plane is referred to here as “skew” or “skew angle”. In oneembodiment, a control system coordinates the use of a skew angle togenerate forces between certain contacting components in the variatorthat will tilt the planet axis of rotation. The tilting of the planetaxis of rotation adjusts the speed ratio of the variator. In thedescription that follows, a coordinate system is established withrespect to the traction planet, followed by a discussion of certainkinematic relationships between contacting components that generateforces which tend to cause the planet axis to tilt in the presence of askew angle. Embodiments of skew control systems for attaining a desiredspeed ratio of a variator will be discussed.

Turning now to FIGS. 1A and 1B, coordinate systems will be defined inreference to embodiments of certain components of a continuouslyvariable transmission (CVT). The coordinate systems are shown here forillustrative purposes and should not be construed as the only frame ofreference applicable to the embodiments discussed here. An embodiment ofa CVT 100 includes generally spherical traction planets 108 in contactwith a traction sun 110. The traction planets 108 are also in contactwith a first traction ring 102 and a second traction ring 104 at,respectively, a first angular position 112 and a second angular position114. A global coordinate system 150 (that is, x_(g), y_(g), z_(g)) and aplanet-centered coordinate system 160 (that is, x, y, z) are defined inFIG. 1A. The global coordinate system 150 is generally oriented withrespect to a longitudinal axis or main drive axis 152 of the CVT 100,for example with the z_(g)-axis coinciding with the main drive axis 152about which the traction planets 108 are arranged. The planet-centeredcoordinate system 160 has its origin at the geometric center of thetraction planet 108 with the y-axis generally bisecting the angle formedbetween the traction rings 102, 104 and the z-axis generally parallel tothe main drive axis 152. Each of the traction planets 108 has an axis ofrotation, that is, a planet axis 106, which can be configured to tilt inthe y-z plane to thereby form a tilt angle 118 (sometimes referred tohere as γ). The tilt angle 118 determines the kinematic speed ratiobetween the traction rings 102, 104. Each of the planets 108 has arotational velocity about the planet axis 106 and is shown in FIG. 1A asplanet velocity 122, sometimes referred to here as ω. Typically theplanet axis 106 corresponds to a planet axle, which is operationallycoupled to a carrier or a cage (not shown) that can be stationary, whilein other embodiments the planet axle is coupled to a carrier (not shown)that is rotatable about main drive axis 152. In the planet-centeredcoordinate system 160, the x-axis is directed into the plane of the pageand the z-axis is generally parallel to the main drive axis 152,consequently the tilt angle 118 is generally coplanar with the maindrive axis 152.

Turning now to FIG. 1B, the planet-centered coordinate system 160 isresolved further to illustrate the angular adjustments of the planetaxis 106 that are used in the embodiments of skew control systemsdescribed here. As shown in FIG. 1B, a tilt angle 118 can be derived byrotating the coordinate system 160 with the planet axis 106 in the y-zplane about the x-axis to achieve a first relative coordinate system 170(x′, y′, z′). In the relative coordinate system 170, the planet axis 106coincides with the z′-axis. By rotating the coordinate system 170 withthe planet axis 106 about the y′-axis, a skew angle 120 (sometimesreferred to here as can be obtained in a x′-z′ plane, which is definedin a second relative coordinate system 180 (x″, y″, z″). The skew angle120 can be considered, approximately, the projection in the x-z plane ofthe angular alignment of the planet axis 106. More specifically,however, the skew angle 120 is the angular position of the planet axis106 in the x′-z′ plane as defined by the relative coordinate systems 170and 180. The skew angle 120 is generally not coplanar with the maindrive axis 152. In some embodiments of the CVT 100, the tilt angle 118can be adjusted directly to adjust the speed ratio. In one embodiment ofthe CVT 100, the tilt angle 118 is controlled, at least in part, throughan adjustment of the skew angle 120.

Referring now to FIG. 1C, certain kinematic relationships betweencontacting components of the CVT 100 will be described to explain howthe inducement of a skew condition generates forces that tend to adjustthe tilt angle 118. As used here, the phrase “skew condition” refers toan arrangement of the planet axis 106 relative to the main drive axis152 such that a non-zero skew angle 120 exists. Hence, reference to“inducement of a skew condition” implies an inducement of the planetaxis 106 to align at a non-zero skew angle 120. It should be noted thatin certain embodiments of the CVT 100 certain spin-induced forces alsoact on the traction plane 108. Spin is a phenomenon of traction contactswell known to those of ordinary skill in the relevant technology. Forour immediate discussion, the effects of the spin-induced forces will beignored. However, later on, embodiments of CVTs will be disclosed thattake into account the effects of spin-induced forces upon the tractionplanet 108 and components operationally coupled to the traction planet108. In the CVT 100, components contact the traction planet 108 at threelocations to form traction or friction contact areas. The first ring 102drives the planet 108 at a contact 1, and the planet 108 transmits powerto the second ring 104 at a contact 2. The traction sun 110 supports thetraction planet 108 at a contact 3. For discussion purposes, the threecontacts 1, 2, 3 are arranged in FIG. 1C to reflect a view of the x″-z″plane as seen from a reference above the CVT 100, or View A in FIG. 1A.Since the contact areas 1, 2, 3 are not coplanar, contact-centeredcoordinate systems are used in FIG. 1C so that the contact areas 1, 2, 3can be illustrated with the x″-z″ plane. Subscripts 1, 2, and 3 are usedto denote the specific contact area for contact-centered coordinatesystems. The z_(1,2,3)-axis are directed at the center of the tractionplanet 108.

Referring now to contact area 1 in FIG. 1C, the surface velocity of thefirst traction ring 102 is denoted in the negative x₁ direction by avector V_(r1) and the surface velocity of the planet 108 is representedby a vector V_(p1); the angle formed between the vectors V_(r1) andV_(p1) is the skew angle 120. The resulting relative surface velocitybetween the traction ring 102 and the traction planet 108 is representedby a vector V_(r1/p). At the contact area 3 between the traction planet108 and the traction sun 110, the surface velocity of the traction sun110 is represented by a vector V_(sv) and the surface velocity of thetraction planet 108 is represented by a vector V_(ps); the angle formedbetween V_(sv) and V_(ps) is the skew angle 120. The relative surfacevelocity between the traction planet 108 and the traction sun 110 isrepresented by a vector V_(sv/p). Similarly, for contact 2, the surfacevelocity of the traction planet 108 at the contact area 2 is shown as avector V_(p2) and the surface velocity of the second traction ring 104is represented by a vector V_(r2); the angle formed between V_(p2) andV_(r2) is the skew angle 120; the relative surface velocity between thetraction planet 108 and the second traction ring 104 is the resultantvector V_(r2/p).

The kinematic relationships discussed above tend to generate forces atthe contacting components. FIG. 1D shows a generalized, representativetraction curve that can be applied at each of contact areas 1, 2, 3. Thegraph illustrates the relationship between the traction coefficient μand the relative velocity between contacting components. The tractioncoefficient μ is indicative of the capacity of the fluid to transmit aforce. The relative velocity, such as V_(r1/p), can be a function of theskew angle 120. The traction coefficient μ is the vector sum of thetraction coefficient in the x-direction μ_(x) and the tractioncoefficient in the y-direction μ_(y) at a contact area 1, 2, or 3. As ageneral matter, the traction coefficient μ is a function of the tractionfluid properties, the normal force at the contact area, and the velocityof the traction fluid in the contact area, among other things. For agiven traction fluid, the traction coefficient μ increases withincreasing relative velocities of components, until the tractioncoefficient μ reaches a maximum capacity after which the tractioncoefficient μ decays. Consequently, in the presence of a skew angle 120(that is, under a skew condition), forces are generated at the contactareas 1, 2, 3 around the traction planet 108 due to the kinematicconditions. Referring to FIGS. 1C and 1E, V_(r1/p) generates a forceF_(s1) parallel to the V_(r1/p). Increasing the skew angle 120 increasesthe V_(r1/p) and, thereby, increases the force F_(s1) according to thegeneral relationship shown in FIG. 1D. The V_(sv/p) generates a forceF_(ss), and similarly, the V_(r2/p) generates a force F_(s2). The forcesF_(s1), F_(ss), and F_(s2) combine to create a net moment about thetraction roller 108 in the y-z plane. More specifically, the summationof moments about the traction roller 108 is ΣM=R*(F_(s1)+F_(s2)+F_(ss)),where R is the radius of the traction roller 108, and the forces F_(s1),F_(s2), and F_(ss) are the resultant components of the contact forces inthe y-z plane. The contact forces, some times referred to here asskew-induced forces, in the above equation are as follows:F_(s1)=μ_(γ1)N₁, F_(s2)=μ_(γ2)N₂, F_(ss)=μ_(γs)N₃, where N_(1,2,3) isthe normal force at the respective contact area 1, 2, 3. Since thetraction coefficient μ is a function of relative velocity betweencontacting components, the traction coefficients μ_(γ1), μ_(γ2), andμ_(γs) are consequently a function of the skew angle 120 as related bythe kinematic relationship. By definition, a moment is the accelerationof inertia; hence, in the embodiment illustrated here, the moment willgenerate a tilt angle acceleration γ″. Therefore, the rate of change ofthe tilt angle γ′ is a function of the skew angle 120.

As already mentioned, spin-induced forces can be generated at thecontacting areas. The spin-induced forces tend to resist theskew-induced forces. During operation of a CVT, the spin-induced forcesand the skew-induced forces can be reacted axially through the tractionsun 110, and are sometimes referred to here as axial forces or sideforces. Embodiments of the CVT 100 can be configured such that theplanet axis 106 tilts when the skew-induced forces are larger than thespin-induced forces. In one embodiment of a CVT, under a steady stateoperating condition, the skew-induced forces and the spin-induced forcescan balance each other, resulting in the CVT operating under a skewcondition. To operate the CVT under a substantially zero skew angle,therefore, it is preferable to provide an auxiliary side force reactionacting on the traction sun 110; that is, in some embodiments of the CVT,the axial position of the traction sun 110 is constrained axially by amechanism other than the skew-induced forces.

Turning now to FIG. 1F, a traction planet 108 is illustrated having atilt angle 118 equal to zero, which results in the planet axis 106 beinggenerally coplanar to the main drive axis 152 of the CVT 100 and therotational velocity 122 of the traction planet 108 is coaxial with thez-axis. A skew angle 120 can be formed in the x-z plane to generateforces for motivating a change in the tilt angle 118. In the presence ofthe skew angle 120, the traction planet 108 would have a rotationalvelocity 122 about an axis z″, and the tilt angle 118 would be formed inthe y-z′ plane.

Passing now to FIGS. 2-5B, embodiments of certain control systems for aCVT that rely on inducing a skew condition to motivate a change in thetilt angle 118 will be described now. FIG. 2 shows a drive 25 thatincludes a CVT 300 operationally coupled between a prime mover 50 and aload 75. The drive 25 can also include a skew-based control system 200.Typically, the prime mover 50 delivers power to the CVT 300, and the CVT300 delivers power to a load 75. The prime mover 50 can be one or moreof various power generating devices, and the load 75 can be one or moreof various driven devices or components. Examples of the prime mover 50include, but are not limited to, human power, engines, motors and thelike. Examples of loads include, but are not limited to, drivetraindifferential assemblies, power take-off assemblies, generatorassemblies, pump assemblies, and the like. In some embodiments, the skewcontrol system 200 can coordinate the operation of the CVT 300 as wellas the prime mover 50, or can coordinate the operation of the CVT 300and the load 75, or can coordinate the operation of all elements in thedrive apparatus 25. In the embodiment illustrated in FIG. 2, the skewcontrol system 200 can be configured to use an adjustment of a skewangle 120 to control the operating condition of the CVT 300, andconsequently, coordinate the control of the drive 25.

Turning to FIG. 3, an embodiment of a CVT 301 will be described now. Forclarity and conciseness of description, only certain components of avariator or CVT are shown. In the embodiment illustrated, a skew lever302 can be operationally connected to carrier plate 304 in such a mannerthat a rotation of the skew lever 302 causes a rotation of the carrierplate 304 with respect to a main axle 312. A second carrier plate 306 isrigidly coupled to the main axle 312. A traction planet assembly 311 anda traction sun assembly 310 are arranged to operate between the twocarrier plates 304 and 306. One end of the planet axis 106 is operablycoupled to the carrier plate 304, and the other end of planet axle 106is operably coupled to the carrier plate 306. The planet-centeredcoordinate system 160 is shown in the planet assembly 308 in FIG. 3 forreference. An angular rotation of the skew lever 302 causes a rotationof the carrier plate 304 to a carrier plate angle 324 (sometimesreferred to as carrier plate angle β. Since the planet axis 106 isconstrained by the carrier plates 304 and 306, the planet axis 106 willadjust to a position that is no longer coplanar with the axis of themain axle 312; resulting in the inducement of a skew condition.

For some applications, a linear relation between an axial translation ofthe traction sun 310 and the tilt angle 118 can be expressed as follows.Axial translation of the traction sun 310 is the mathematical product ofthe radius of the traction planets 308, the tilt angle 18 and a RSF(that is, axial translation of the traction sun 310=planet radius*tiltangle 118*RSF), where RSF is a roll-slide factor. RSF describes thetransverse creep rate between the traction planet 308 and the tractionsun 310. As used here, “creep” is the discrete local motion of a bodyrelative to another and is exemplified by the relative velocities ofrolling contact components as previously discussed. In traction drives,the transfer of power from a driving element to a driven element via atraction interface requires creep. Usually, creep in the direction ofpower transfer is referred to as “creep in the rolling direction.”Sometimes the driving and driven elements experience creep in adirection orthogonal to the power transfer direction, in such a casethis component of creep is referred to as “transverse creep.” Duringoperation of the CVT 301, the traction planet 308 and the traction sun310 roll on each other. When the traction sun 310 is translated axially(that is, orthogonal to the rolling direction), transverse creep isimposed between the traction sun 310 and the traction planet 308. An RSFequal to 1.0 indicates pure rolling. At RSF values less than 1.0, thetraction sun 310 translates slower than the traction planet 308 rotates.At RSF values greater than 1.0, the traction sun 310 translates fasterthan the traction planet 308 rotates.

Turning now to FIG. 4, an embodiment of a skew-based control system 205that can be used with the drive 25 will be described now. In oneembodiment, the skew-based control system 205 can include a skewdynamics module 202, which can be defined by a transfer function, forexample. The skew dynamics module 202 abides by the kinematicrelationships described previously between a skew angle 120 and thegeneration of forces that tend to motivate an adjustment in the tiltangle 118. In some embodiments, the operating condition of the CVT 300,or substantially equivalent embodiments, can be used as input for theskew dynamics module 202 and can be generally represented by the normalforce (that is, F_(N)) at the contact areas and the rotational velocityω of the traction planet 308. A control reference 208 can be a desiredskew angle 120, for example. The control reference 208 is compared to afeedback value 201 at the summing junction 210. The feedback value 201is indicative of an actual skew angle under the current operatingconditions. The resulting skew angle ζ is provided to the skew dynamicsmodule 202, which returns a rate of change in the tilt angle γ′;integration of γ′ with integrator 204 returns a tilt angle γ. In oneembodiment, the tilt angle γ is further processed by a gain (K) 2050 toprovide feedback to the summing junction 210. In some embodiments, thecontrol reference 208 can be a position reference of the traction sun110, a desired tilt angle γ, or any other parameter relevant to theoperation of the CVT 300, such as a speed ratio or a torque ratio. Incertain embodiments, the control reference 208 can be converted whereappropriate to provide a reference skew angle ζ_(R).

Referring to FIG. 5A, an embodiment of a skew control system 206 will bedescribed now. The control reference 208 can be an angular positionreference such as a rotation of a shift nut or a reference dial, whichis coupled to a planetary gear set having a ratio (K₁) 500. An angularposition of a planetary gear set can be transformed into an axialtranslation of a reference element by using, for example, a screw lead(K₂) 502, and can be compared to an axial position of a traction sun 110(again, for example) to derive a control error 408. In some embodiments,an axial position, such as the axial position of a shift rod (notshown), can be used as the control reference 208. In the embodimentshown in FIG. 5A, the control reference 208 is compared to a feedback404, which in this case is the axial position of the traction sun 110,at the summing junction 412 to derive the control error 408. It ispreferable to convert the physical units of the control reference 208and the feedback 404 so that the two parameters have the same unitsprior to the summing junction 412 for arithmetic consistency. A gain(K₃) 406 can be applied to convert the control error 408 into a carrierplate angle β, such as the carrier plate angle 324 shown in FIG. 3, forexample. In some embodiments, the gain 406 can be a screw lead. Thecarrier plate angle β can be actuated by a skew lever 302 as shown inFIG. 3, for example.

In this embodiment, a skew algorithm 400 includes a function 203 coupledto the skew dynamics module 202. The function 203 is configured toconvert the carrier plate angle β into a skew angle ζ. The skewalgorithm 400 receives the carrier plate angle β as input and returns arate of change in tilt angle γ′. In one embodiment, an integrator 410can be applied to the result of the skew dynamics module 202 to derive atilt angle γ, which determines a speed ratio of a CVT. A speed ratio(SR) 420 can be derived from γ by a function 418 having as inputs thenormal force F_(N) and the rotational speed of the traction planet 108.The tilt angle γ can also be transformed into a feedback 404 by applyinga gain (K4) 402. In some embodiments, the gain 402 is equal to theplanet radius multiplied by the RSF (that is, K4=R*RSF). In oneembodiment, the skew algorithm 400 is a transfer function based on thespecific operating conditions of a CVT. In some applications, the skewalgorithm 400 can take the form of a look up table that can be createdby empirically determining γ′ for a given carrier plate angle β andoperating conditions of a CVT. For example, tests can be performed on aspecific CVT where the input operating condition is held at discretespeeds and loads appropriate for the intended application, whilediscrete steps in the carrier plate angle β can be applied to the systemso that the speed ratio change of the CVT can be measured and used tocalculate the resultant γ′. The resultant data characterizes the dynamicresponse of the system and can be formulated into a look-up table orfunction used for the skew algorithm 400.

Referring now to FIG. 5B, yet another embodiment of a skew-based controlsystem 207 that can be used with the drive 25 will be described now. Fordescription purposes the skew control system 207 will be described byanalogy to a mechanical embodiment such as the one shown in FIG. 6;however, in some embodiments, the skew control system 207 can beimplemented as an electrical or electro-mechanical system where theelements shown in FIG. 5B are functions in an electronic controller. Theskew control system 207 includes the control reference 208 coupled to aplanetary gear set having a ratio (K₁) 500. In some embodiments, thecontrol reference 208 can be adjusted by the application of a torque 209to the shift nut or reference dial. The control reference 208 appliedwith a torque 209 can be transformed into an axial translation of areference element, such as a feedback cam 1066 having a screw lead (K₂)502.

In one embodiment, the skew control system 207 includes two summingjunctions 501 and 503. The first summing junction 501 produces thecontrol error 408 based on a control reference 208 and two sources offeedback. A first feedback source can be the axial position of thetraction sun 110, and the other feedback source can be the axialposition of the skew cam 1068 (see FIG. 6), for example. The secondsumming junction 503 sums forces exerted on the skew cam 1068. Theresult of the summing junction 503 is, therefore, a force exerted on theskew cam 1068 that can be used to determine the axial position of theskew cam 1068. The position χ of the skew cam 1068 is determined bydividing the resultant force of the summing junction 503 by the mass ofthe skew cam 1068, shown as gain 508, and integrating the resulting skewcam acceleration χ″ with integrators 410, once to determine speed χ′ ofthe skew cam 1068 and again to determine the position χ. The axialposition χ is provided as input to the summing junction 501 and combinedwith the control reference 208 and the axial position of the tractionsun to derive a control error 408. A gain (K₃) 406 can be applied toconvert the control error 408 into a carrier plate angle β. The skewalgorithm 400 receives a carrier plate angle β as input and returns arate of change in tilt angle γ′. An integrator 410 is applied to γ′ toprovide a tilt angle γ that can be further transformed into an axialposition of traction sun by applying a gain (K₄) 402. The gain 402 isequal to the planet radius multiplied by the RSF (that is, K₄=R*RSF).

Referring still to FIG. 5B, the summing junction 503 will be describedfurther. As previously stated, the summing junction 503 sums forcesexerted on, for example, the skew cam 1068. The forces can includefriction 510, neutralizing spring force 512, control reference force514, carrier plate force 516, and axial forces 518 on the traction sun110, 1026, which is typically produced at the contact area 3 between thetraction sun 110, 1026 and the traction planet 108, 1022, for example.For the embodiment shown, friction exerted on the skew cam 1068 can bedetermined from the velocity of the skew cam 1068 and the screw lead ofthe skew cam 1068 with a function 511. Neutralizing spring force 512 canbe determined by applying a gain (K₅) 513 to the control error 408formed at the summing junction 501. In some embodiments, the gain (K₅)513 can represent a mechanical system that tends to bias a skew cam1068, for example, to a neutral location through linear, non-linear, ordiscontinuous functions, such as the neutralizer assembly 1092 shown inFIG. 6. A force can be generated by the reference torque 209 exertedwhile adjusting the control reference 208. In one embodiment, thecontrol reference force 514 is determined by applying a gain (K₆) 515proportional to the effective lever arm of the torque 209 applied to theskew cam 1068. During operation of a CVT 300, for example, the drivetorque (τ) 521 is reacted by the carrier plates 304 and 306. In someembodiments, the carrier plate 304 can be configured to react the drivetorque (τ) 521 and to actuate the skew angle ζ, for instance, by a skewlever 302 or a skew cam 1068. In one embodiment, the carrier platetorque function 520 provides a carrier plate torque 522 based on thedrive torque (τ) 521 and the tilt angle γ. The resulting carrier plateforce 516 acting on the skew cam 1068 is determined by applying to thecarrier plate torque 522 a gain (K₇) 517, which is proportional to thedistance from the skew cam 1068 that the carrier plate torque is actingon the skew cam 1068.

The axial force 518 on the traction sun is reacted on the skew cam 1068in some embodiments. In one embodiment, the axial force 518 is generatedby spin-induced and skew-induced side forces at the contact area 3. Theforce 518 can be determined by the traction sun force algorithm 519 thatis a function of, among other things, the normal force at contact 3 andthe rotational speed ω of the traction planet 108, 308, or 1022. Theforces just described are combined at the summing junction 503 and areused in the skew control system 207 for feedback to account for thesteady state operating error that can exist in the skew angle ζ. Asteady state error in the skew angle ζ can arise when operating the CVT300 due to reacting the spin-induced side forces on the traction sun. Insome embodiments, it is preferable for optimal efficiency of a CVT togenerally operate with a skew angle ζ equal to zero when a change inspeed ratio is not desired. The embodiment of a skew control systemshown in FIG. 6 incorporates a side force neutralizer assembly 1092 thateffectively reacts the side forces on the traction sun 1026 so that theskew angle ζ is at an optimal operating skew condition ζ_(opt), which insome cases means a substantially zero skew angle ζ during steady stateoperation.

Passing now to FIG. 5C, another embodiment of a skew control system 2000is described. As previously discussed, during operation of a CVT 300 asteady state error of the skew angle ζ can arise due to axial forcesacting on the traction sun. Therefore, to maintain a steady state speedratio, it is desirable to decouple the skew control system 2000 from theposition of the traction sun. In one embodiment, a traction sun positionlocker 530 can be coupled to a traction sun and integrated with the skewcontrol system 2000. The traction sun position locker 530 can be, forexample, a mechanism that locks and holds the traction sun at an axialposition until the lock is released. The mechanism can be a mechanicallocking pawl, or an electro-mechanically actuated device, or anelectro-hydraulically actuated device.

In one embodiment, the state of the traction sun position locker isbased on a result from a decision process 532 that compares the controlerror 408 with an upper and lower limit for the error. If the controlerror 408 is within the limits set in the decision process 532, thepositive or true result from the process 532 is sent to the traction sunposition locker 530, which returns a command 531 to lock the tractionsun at its current position. A positive or true result from the decisionprocess 532 is also sent to a skew angle ζ coordinator 534 that returnsa command 536 to set the skew angle ζ to an optimal skew angle ζ_(opt),which is some embodiments it means that the skew angle ζ is zero. If thecontrol error 408 is not within the limits of the decision process 532,a negative or false result is passed to the sun position locker 530,which returns a command 533 to unlock the traction sun. The false resultis passed to the skew angle ζ coordinator 534, which returns a command537 that passes the control error 408 to, for example, a skew algorithm400, to execute a change in the tilt angle γ. In this embodiment, thecontrol error 408 can be determined by comparing a control reference 208to a feedback 404. A control reference 408 can be a position, eitherangular or axial, a desired speed ratio, or any other relevant referencefor operating a CVT 300.

The embodiments of a skew-based control system described previously canbe used in conjunction with systems such as speed governors or torquegovernors, among others. In applications were it is desirable tomaintain a constant input speed in the presence of a varying outputspeed, or vice versa, a mechanical, electrical, or hydraulic speedgovernor can be coupled to the shift nut or control reference in orderto adjust the operating condition of the drive. In other applications,it might be desirable to maintain a constant input torque in thepresence of a varying output torque, which is generally more challengingto implement with traditional controls systems. A skew control system,such control system 200 described here, can be coupled to a mechanismfor controlling input torque in the presence of a varying output torque.

A CVT 1000 adapted to employ a skew-based control system related tothose discussed above will now be described with reference to FIGS.6-23. In one embodiment, the CVT 1000 includes a housing formedgenerally by a shell 1010 and a cap 1012; the shell 1010 and the cap1012 can be rigidly coupled with, for example, bolts, screws, or athreaded joint. A power input member 1014, such as a sprocket forexample, couples to an input driver 1018, which is positioned coaxiallywith a longitudinal axis LA1 of the CVT 1000. A first axial forcegenerator 1016 is placed between the input driver 1018 and a firsttraction ring 1020. An array of traction planets 1022 is positioned on aplane perpendicular to the longitudinal axis LA1. The traction planets1022 are arranged angularly about the longitudinal axis LA1, and areplaced in frictional or tractive contact with the first traction ring1020, a second traction ring 1024, and a traction sun 1026. The shell1010 is adapted to receive torque from, or transmit torque to, thesecond traction ring 1024. In one embodiment, a shell torque member 1028couples to the second traction ring 1024 via a second axial forcegenerator 1030. The traction ring 1024, traction sun 1026, and the axialforce generators 1016, 1030 are mounted coaxially with the longitudinalaxis LA1. In some embodiments, the shell 1010 and the cap 1012 aresupported radially by bearings 1032, 1034, respectively. The bearing1032 provides a rolling interface between the shell 1010 and an axialretainer plate 1084. The bearing 1034 provides a rolling interfacebetween the cap 1012 and the input driver 1018. A thrust bearing 1036can be positioned between the input driver 1018 and the cap 1012 toprovide an axial rolling interface between the input driver 1018 and thecap 1012, which cap 1012 reacts axial forces generated during operationof the CVT 1000. A main axle 1038 can be provided to, in part, supportvarious component of the CVT 1000 and to, in some embodiments, providefor attachment of the CVT 1000 to a frame of a vehicle, a supportbracket, a fixed member of a machine, or the like.

The CVT 1000 includes carrier plates 1040, 1042 adapted to, among otherthings, support radially and axially an array of planet-leg assemblies1044, which will be described further with reference to FIGS. 9 and 10.In some embodiments, stator spacers (not shown) can be provided toattach the carrier plates 1040, 1042 together. Preferably, for certainapplications, the carrier plates 1040, 1042 are coupled onlysemi-rigidly (rather than rigidly) to allow some relative rotationbetween the carrier plate 1040 and the carrier plate 1042. As will bedescribed further below, in some embodiments, at least one of thecarrier plates 1040, 1042 can be adapted to facilitate adjustment of thespeed ratio of the CVT 1000.

Referring to FIGS. 9 and 10 specifically now, a planet-leg assembly 1044generally includes, among other things, a traction planet 1022 mountedabout a planet axle 1046. In some embodiments, one or more bearings 1048can be provided between the planet axle 1046 and a bore of the tractionplanet 1022. The planet axle 1046 is configured to extend beyond thecircumference of the traction planet 1022. At each end of the planetaxle 1046, a leg 1050 couples to the planet axle 1046. The leg 1050 issometimes characterized as a shift lever because the leg 1050 acts as alever to facilitate a tilt of the planet axle 1046, which results in anadjustment (or shift) of the speed ratio between the traction rings1020, 1024. In some embodiments, the leg 1050 is adapted to receive andsupport a shift cam roller 1052 and a shift guide roller 1054. The shiftcam rollers 1052 are adapted to transmit force from shift cams 1056,1058 (see FIG. 6) to the legs 1050 for, among other things, facilitatinga speed ratio adjustment. In some embodiments, the shift guide rollers1054 are generally adapted to cooperate with the carrier plates 1040,1042 to react forces that arise during a speed ratio adjustment. In oneembodiment, each of the planet axles 1046 is provided with a skew roller1060 to, in part, react forces that tend to misalign (that is, removethe coplanarity between) a longitudinal axis of the planet axle 1046 andthe longitudinal axis LA1. It should be noted that the planet-legassembly 1044 described here is merely one example of a variety ofplanet-leg assemblies that can be used with the CVT 1000. Other suitableplanet-leg assemblies and/or legs, are described in U.S. PatentApplication 60/943,273, filed on Jun. 11, 2007, and which is herebyincorporated by reference herein in its entirety.

During operation, referencing FIG. 6 most particularly, the flow ofpower through the CVT 1000 proceeds generally as follows. Power is inputto the power input member 1014. The input driver 1018 receives the powerfrom the input member 1014 and drives the axial force generator 1016.Power flows from the axial force generator 1016 into the first tractionring 1020, which through friction or traction drives the tractionplanets 1022. The second traction ring 1024 receives power from thetraction planets 1022 and transfers power to the second axial forcegenerator 1030. Power flows from the second axial force generator 1030to the shell 1010 via the shell torque member 1028. Power can then bedelivered from the shell 1010 to a load, final drive, machine, gearbox,planetary gearset, etc. It should be noted that the power flow justdescribed can be reversed such that power is input via the shell 1010and transmitted from the second axial force generator 1030, to thesecond traction ring 1024, and so on, and delivered to the power inputmember 1014 (in which case, the power input member 1014 is moreprecisely characterized as a power output member). It should beadditionally noticed that in some applications it might be preferable toprovide a power output shaft (not shown) that can be coupled to thesecond axial force generator 1030, which allows the shell 1010 to beremoved from the power flow and to be held stationary relative to thepower flow components.

Adjustment in the speed ratio between the traction rings 1020, 1024,which adjustment results in the modulation of power flow through the CVT1000, can be accomplished by tilting the axis of the planet axles 1046relative to the longitudinal axis LA1. In the discussion that follows,mechanisms and methods for actuating and controlling a tilting of theplanet axles 1046 will be described.

Referencing FIGS. 6-8 and 13-23 more specifically now, in one embodimenta reference input nut 1062 is mounted coaxially with the longitudinalaxis LA1 and coupled via a sliding spline interface 1064 to a feedbackcam 1066. The sliding spline interface 1064 is configured to allow thereference input nut 1062 to rotate the feedback cam 1066, and to allowthe feedback cam 1066 to translate axially relative to the referenceinput nut 1062. A skew cam 1068 includes a first threaded portion 1070adapted to couple to a mating threaded portion 1122 of the feedback cam1066 (see FIGS. 15-18). The skew cam 1068 additionally includes a secondthreaded portion 1072 configured to mate with a corresponding threadedportion 1074 of the carrier plate 1042. In one embodiment, the main axle1038 is provided with a splined portion 1076 that mates to a splinedportion 1082 of the skew cam 1068. The splined interface between themain axle 1038 and the skew cam 1068 facilitates anti-rotation, butallows relative axial translation, of the skew cam 1068 relative to themain axle 1038. In some embodiments, the reference input nut 1062,feedback cam 1066, and skew cam 1068 are mounted concentrically with themain axle 1038.

To adjust a speed ratio of the CVT 1000, the reference input nut 1062 isturned to a selected position indicative of a desired speed ratio. Ifthe axial forces (or, in other words, the clamping load provided by theaxial force generators that yield a normal force at the contact) on thetraction planets 1022 is relatively low or substantially zero, throughthe splined interface 1064 the reference input nut 1062 causes thefeedback cam 1066 to rotate about the longitudinal axis LA1. Hence, whenthe clamp loads on the traction planets 1022 are relatively low, theskew cam 1068 tends not to translate. Consequently, the feedback cam1066 is forced to translate axially as the feedback cam 1066 rotatesabout the axis LA1. The axial translation of the feedback cam 1066causes an axial translation of the traction sun 1026 via thrust bearings1078, 1080. Axial translation of the traction sun 1026 results in atilting of the planet axles 1046 through the operational couplingbetween the traction sun 1026 and the planet axles 1046 via the shiftcams 1056, 1058, shift cam rollers 1052, and legs 1050.

When the clamp loads on the traction planets 1022 are at, for example,average operating conditions, rotation of the reference input nut 1062causes a rotation of the feedback cam 1066; however, under thisoperating condition, the resistance provided by the planet-legassemblies 1044 and the shift cams 1056, 1058 tend to constrain axialtranslation of the feedback cam 1066. Since the feedback cam 1066rotates but does not translate, the skew cam 1068 (which is constrainedrotationally via the sliding spline portion 1082) is forced to translateaxially via the threaded interface 1070, 1122 between the feedback cam1066 and the skew cam 1068. Since the carrier plate 1042 is constrainedaxially but can have at least some angular rotation, the carrier plate1042 is urged into angular rotation about the longitudinal axis LA1through the sliding spline interface 1072, 1074 between the skew cam1068 and the carrier plate 1042, resulting in the carrier plate 1042inducing the planet axles 1046 into a skew condition. In one embodiment,the carrier plate 1042 rotates angularly until a maximum skew angle isachieved. The skew condition, as explained above, causes a tilting ofthe planet axles 1046. The tilting of the planet axles 1046 results inan adjustment of the speed ratio of the CVT 1000. However, the tiltingof the planet axles 1046 additionally acts to translate axially theshift cams 1056, 1058 via the operational coupling between the planetaxles 1046 and the shift cams 1056, 1058. The axial translation of theshift cams 1056, 1058 consequently results in an axial translation ofthe feedback cam 1066 via the thrust bearings 1078, 1080. Since thereference input nut 1062 prevents rotation of the feedback cam 1066, theskew cam 1068 and the feedback cam 1066 translate axially together. Theaxial translation of the skew cam 1068 causes a restoring angularrotation upon the carrier plate 1042, which consequently returns to askew angle that generates sufficient skew forces to maintain the skewcam 1068 at an equilibrium axial position.

When the CVT 1000 is under an operation condition that is between a noload condition and a loaded condition, there can exist a cross overcondition under which inducement of a skew condition of the planet axles1046 (as well as the restoring action to zero skew condition) involves atranslation and a rotation of the feedback cam 1066 with a simultaneoustranslation of the skew cam 1068. In all cases, the feedback cam 1066and the skew cam 1068 are configured to cooperate to induce a skewcondition of the planet axles 1046 via an angular rotation of thecarrier plate 1042. The skew condition causes a tilting of the planetaxles 1046 to set the CVT 1000 at a desired speed ratio. The feedbackcam 1066, under action from the planet-leg assemblies 1044, cooperateswith skew cam 1068 to restore the carrier plate 1042 to a position thatinduces a nominal zero skew.

Referring now to FIGS. 11 and 12 more specifically now, in oneembodiment, the carrier plate 1042 is constrained axially by the axialretainer plate 1084 and an axial retainer cap 1086, which cooperate withthrust bearings 1088, 1090, as shown in Detail View B of FIGS. 6 and 12.The axial retainer plate 1084, axial retainer cap 1086, and the thrustbearings 1088, 1090 are mounted coaxially about the longitudinal axisLA1, and are configured to facilitate an axial constraint of the carrierplate 1042 while allowing an angular rotation of the carrier plate 1042about the longitudinal axis LA1. The axial retainer plate 1084 ispreferably coupled rigidly to the main axle 1038; that is, the retainerplate 1084 is configured in some embodiments to be constrained axially,radially, and rotationally relative to the longitudinal axis LA1. In oneembodiment, the carrier plate 1040 is constrained axially, radially, androtationally relative to the longitudinal axis LA1, which constrains canbe achieved by, for example, coupling rigidly the carrier plate 1040 tothe main axle 1038. In some embodiments, the interface between thecarrier plate 1040 and the input driver 1018 is provided with a rollingbearing surface, or bearings, to allow relative rotation between thecarrier plate and the input driver 1018 with minimal friction.

Because of the nature of a ball planetary drive such as the CVT 1000,the traction sun 1026 tends to be subjected to an axial force (also,referred to as a “spin-induced side force”) through the contact betweenthe traction planets 1022 and the traction sun 1026 during operation ofthe CVT 1000. When such an axial force is not counteracted, it ispossible that the traction sun 1026 will tend to induce an axialtranslation of the skew cam 1068, resulting in operation at a non-zeroskew angle.

In the embodiment of the CVT 1000 illustrated, the spin-induced sideforce on the traction sun 1026 is balanced, at least in part, by askew-induced side force; hence, the skew cam 1068 is held inequilibrium. However, such a configuration produces a steady statenon-zero skew angle condition, which can be less efficient than a zeroskew angle condition. To achieve a zero skew angle condition, thespin-induced side forces are preferably balanced by a force other than askew-induced side force.

In one embodiment, the CVT 1000 can be provided with a side forceneutralizer assembly 1092, which is generally shown in Detail A view ofFIGS. 6 and 11. In some embodiments, the neutralizer 1092 includes afirst resistance member 1094 (such as one or more coil springs, wavesprings, belleville springs, etc.) positioned between the axial retainerplate 1084 and a translating resistance cup 1096. The first resistancemember 1094 and the translating resistance cup 1096 are mounted adjacentto one another and coaxially about the longitudinal axis LA1. Aneutralizer reaction flange 1098 can be coupled to the skew cam 1068.The neutralizer reaction flange 1098 is positioned adjacent to thetranslating resistance cup 1096. A second resistance member 1100 ispositioned between the neutralizer reaction flange 1098 and aneutralizer stop cap 1102 that can be rigidly mounted to the resistancecup 1096, all of which are mounted coaxially about the longitudinal axisLA1. Preferably, the neutralizer stop cap 1102 is axially constrainedby, for example, the carrier plate 1042.

During operation, as the side force tends to induce an axial translationof the traction sun 1026, the tendency of the feedback cam 1066 and theskew cam 1068 to translate axially is resisted by either one of theresistance members 1094, 1100. If axial translation of the skew cam 1068is to the left (based on the orientation of the CVT 1000 in FIG. 6), theneutralizer reaction flange 1098 coupled to the skew cam 1068 pushes onthe translating resistance cup 1096. The first resistance member 1094,supported axially by the axial retainer plate 1084, provides acountering force on the neutralizer reaction flange 1098 through thetranslating resistance cup 1096. Hence, the first resistance member 1094is configured to counteract translation of the skew cam 1068 in a firstdirection towards the carrier plate 1042. Similarly, as the skew cam1068 tends to moves in a second direction toward the carrier plate 1040,the second resistance member 1100 is supported axially by theneutralizer stop cap 1102 and provides a counteracting force that tendsto resist the axial translation of the skew cam 1068 in the seconddirection. It should be noted that the translating resistance cup 1096is configured to facilitate a decoupling of the action of the resistancemembers 1094, 1100. The resistance of the resistance members 1094, 1100is appropriately selected to allow a translation of the skew cam 1068 ata desired operation condition of the CVT 1000 when a speed ratioadjustment is desired. Hence, preferably the resistance of theresistance members 1094, 1100 is suitably selected to provide generallyonly the minimum sufficient resistance needed to counteract the sideforce on the traction sun 1026. In some embodiments, the resistancemembers 1094, 1100 can have variable resistance and vary with theoperating condition of CVT 1000, so that the optimal resistance isprovided to the skew cam 1068 to neutralize the forces induced on theskew cam 1068.

Turning now to FIGS. 13 and 14, in one embodiment the main axle 1038includes a generally elongated, cylindrical body 1104. The main axlebody 1104 can be provided with a sliding spline portion 1076, which ispreferably configured to mate to a corresponding sliding spline portion1082 of the skew cam 1068. In some embodiments, the main axle body 1104can exhibit a bearing seat 1106 for receiving and supporting one or moremain axle radial bearings 1108 that provide coaxial support between themain axle 1038 and the skew cam 1068 with minimal sliding friction. Inone embodiment, the main axle 1038 is configured with a bearing seat1110 for receiving and supporting one or more feedback cam bearings 1112that provide coaxial support between the main axle 1038 and the feedbackcam 1066 with minimal sliding friction. In some cases, the bearings1108, 1112 are axial roller bearings, or can be replaced by a slidinginterface between the main axle 1038 and, respectively, the skew cam1068 and feedback cam 1066. In one embodiment, the main axle 1038 can beprovided with a main axle flange 1114 that, among other things, providesa piloting surface 1115 for receiving the reference input nut 1062. Themain axle flange 1114 can have a shoulder 1116 for providing an axialconstraint for the reference input nut 1062.

Passing to FIGS. 15 and 16, in one embodiment, the feedback cam 1066includes a generally elongated, cylindrical, hollow body 1118. A bore1120 of the feedback cam 1066 is configured to allow the feedback cam1066 to be mounted coaxially about the main axle 1038. In oneembodiment, the bore 1120 can exhibit a threaded portion 1122 adapted toengage a corresponding threaded portion 1070 of the skew cam 1068. Oneportion of the feedback cam 1066 is preferably provided with a slidingspline 1124 adapted to mate with a corresponding sliding spline 1064 ofthe reference input nut 1062. In one embodiment, the feedback cam 1066can be provided with one or more bearing races 1126, 1128 to form partof the thrust bearings 1078, 1080 (see FIG. 6).

Referring to FIGS. 17 and 18, in one embodiment, the skew cam 1068includes a generally elongated, hollow, cylindrical body 1130. The skewcam 1068 can be provided with a first threaded portion 1070 adapted toengage a mating threaded portion 1122 of the feedback cam 1066. The skewcam 1068 can be configured additionally with a second threaded portion1072 for engaging a mating threaded portion 1074 of the carrier plate1042. In one embodiment, the lead of the first thread portion 1070 isrelatively smaller than the lead of the second threaded portion 1072;for example, the lead of the first threaded portion 1070 can be about10-30 mm, and the lead of the second threaded portion 1072 can be about100-300 mm. In one case, the leads for the first and second threadedportions 1070, 1072 are, respectively, 20 mm and 200 mm (or, in otherwords, in a ratio of about 1:10). In some embodiments, a neutralizingreaction flange 1098 is formed integral with the skew cam 1068. However,in other embodiments, the neutralizer reaction flange 1098 can beprovided separately and suitably configured to be coupled to the skewcam 1068. A bore 1132 of the skew cam 1068 can be adapted to allow theskew cam 1068 to be mounted about the main axle 1038. In one embodiment,at least a portion of the bore 1132 is provided with a sliding spline1082 configured to mate with a corresponding sliding spline 1076 of themain axle 1038. In some embodiments, the skew cam 1068 can be formedwith a splined portion 1133 on the outer diameter of the body 1130,arranged axially for mating with sliding splines 1144 formed on theshift cam 1056 to facilitate anti-rotation of the shift cam 1056 aboutthe longitudinal axis LA1.

Turning now to FIGS. 19 and 20, in one embodiment, a carrier plate 1042can be generally a plate or frame, mounted coaxially with the main axle1038, for supporting and guiding the skew rollers 1060 and/or the shiftguide rollers 1054. In one embodiment, the carrier plate 1042 includes athreaded central bore 1074 adapted to engage the threaded portion 1072of the skew cam 1068. The carrier plate 1042 includes surfaces 1134 thatare generally concave and are adapted to support the shift guide rollers1054 as the CVT 1000 is shifted. Additionally, the carrier 1042 isprovided with reaction surfaces 1136, angularly arranged about thecentral bore 1074, for reacting forces transmitted through the skewrollers 1060 as the CVT 1000 is in operation. The carrier plate 1042 canbe provided with an outer ring 1137 having on one side a face 1138 andon the other side a face 1140 for mating with thrust bearings 1088 and1090. The carrier plate 1042 can also have a reaction face 1142 tofacilitate the axial constraint of the neutralizer stop cap 1102 in onedirection.

Referring now to FIG. 21, in one embodiment the shift cam 1056 isgenerally a cylindrical body with a splined inner bore 1144 configuredto couple with the sliding spline 1133 of the skew cam 1068. The shiftcam 1056 is provided with a profiled surface 1146 for guiding the shiftcam rollers 1052. Two bearing races 1148 and 1150 are formed into theshift cam 1056 for cooperating with, respectively, the bearing balls ofthe bearing 1080 and the bearing balls supporting the traction sun 1026.

Passing now to FIGS. 22 and 23, a leg assembly 1051, which can be usedwith certain embodiments of a CVT equipped with a skew control system,will be described now. The leg assembly 1051 can include a leg 1053having, on one end, a bore 1152 for receiving the planet axle 1046, andon another end, a slot 1154 to receive the shift cam roller 1052. A bore1156 is formed generally perpendicular to the slot 1154 to retain anaxle (not shown) for securing the shift cam roller 1052. A shift guideroller axle 1158 can be supported in a bore 1160 while being providedwith clearance bores 1162 and 1164. The clearance bores 1162, 1164facilitate proper coupling between shift guide rollers 1159 and skewreaction rollers 1161 and carrier plates 1040, 1042 during a shift ofthe speed ratio induced by a skew condition. The bores 1160, 1162, and1164 are suitably configured to allow a swiveling or pivoting of theshift guide roller axle 1158 about substantially the center of the shiftguide roller axle 1158. The skew reaction rollers 1161 and/or the shiftguide rollers 1159 are preferably provided with a crowned, curvedsurface configured to interface with the carrier plates 1040, 1042 sothat contact is insured between the skew reaction rollers 1161 and/orthe shift guide rollers and the carrier plates 1040, 1042 during ashifting of the ratio of the CVT under a skew condition.

Passing to FIGS. 24-29 now, an alternative embodiment of a CVT 1002 willbe described now. Before proceeding with the description of the CVT1002, however, it will be helpful to refer back to the CVT 1000. In someembodiments of the CVT 1000, where the carrier 1040 is coupled rigidlyto the main axle 1038, it is possible that the reference input nut 1062can only turn about the longitudinal axis LA1 through an arc that isless than 360 degrees. Such a configuration might not be desirable incertain circumstances. In one embodiment, the CVT 1002 is configured toallow a reference input ring 1166 to rotate about the longitudinal axisLA1 through angles greater than 360 degrees. Such functionality allowsfor greater range and resolution in the control of the speed ratio.

The CVT 1002 is substantially similar to the CVT 1000, except in thefollowing aspect which will now be described. To effect a speed ratioadjustment, the reference input ring 1166 is coupled to a feedback cam1168. As depicted best in FIGS. 24 and 25, in one embodiment, thereference input ring 1166 and the feedback cam 1168 are one integralpiece. A rotation of the reference input ring 1166 causes a rotation ofthe feedback cam 1168. The interaction between the feedback cam 1168 andthe skew cam 1068 to induce a skew angle via the carrier plate 1042 issubstantially similar as described above with reference to the CVT 1000.

To rotate the reference input ring 1166, a sun gear shaft 1170 isprovided with a sun gear 1172, which is part of a planetary referenceinput 1174. The sun gear 1172 is coupled to a number of planet gears1176, which are coupled to the reference input ring 1166 in a planetarygear configuration. A planet carrier 1178 of the planetary referenceinput 1174 is rigidly coupled to ground; hence, the planet carrier 1178is constrained axially and rotationally relative to the longitudinalaxis LA1. In one embodiment, the carrier plate 1040 is rigidly coupledto the planetary carrier 1178 via planetary axles 1180, which also serveto support the planet gears 1176. In some instances, the carrier plate1040 can be coupled to the planetary carrier 1178 via a press fit orsplines, for example. In some embodiments, a main axle 1182 can beadapted to couple rigidly to the planet carrier 1178 via the planetaryaxles 1180. Hence, the planetary carrier 1178, the carrier plate 1040,and the main axle 1182 are substantially constrained axially andprevented from rotation about the longitudinal axis LA1. In theembodiment shown in FIG. 24, the carrier plate 1040 is rigidly coupledto a carrier retainer cup 1184, which is the component of the carrierplate 1040 that is rigidly coupled to the planetary carrier 1178. One ormore carrier cup bearings 1186 can be used to provide a rollinginterface between the carrier retainer cup 1184 and an input driver1188.

Referencing FIG. 27 now, in one embodiment, the main axle 1182 can beadapted with a mating flange 1190 having a number of circumferentialmating splines 1192, which are configured to mate correspondingcircumferential splines 1194 (see FIG. 25) of the planetary carrier1178. Hence, in some embodiments, the anti-rotational coupling of themain axle 1182 to the planetary carrier 1178 is assisted by the matingsplines 1192 and 1194. For certain applications, the main axle 1182 andthe planetary carrier 1178 are coupled at raised extensions (similar tothe splines 1192, 1194) in the space between the planet gears 1176. Insuch a configuration, the planet gears 1176 can be inserted between theopenings adjacent to the coupling extensions.

Moving now to FIGS. 28 and 29, the feedback cam 1168 includes a threadedcentral bore 1196 adapted to allow mounting of the feedback cam 1168about the main axle 1182 and to engage mating threads 1070 of the skewcam 1068. The feedback cam 1168 can include bearing races 1126, 1128. Inone embodiment, the feedback cam 1168 is provided with a toothed portion1198 for engaging the planet gears 1176. The toothed portion 1198 ispreferably configured, in some embodiments, to allow axial translationof the feedback cam 1168 relative to the planet gears 1176, whilesimultaneously allowing the feedback cam 1168 to engage the planet gears1176.

Referring now to FIGS. 30-35, a CVT 1004 can be configured similarly tothe CVT 1000 and the CVT 1002; however, in some embodiments, the CVT1004 includes a shift cam 1200 adapted to receive one or moreanti-rotation rods 1204. To prevent rotation of the shift cams 1200,1202 about the longitudinal axis LA1, the anti-rotation rods 1204 arecoupled to the carrier plates 1040, 1042, which are configured to besubstantially non-rotational relative to the longitudinal axis LA1. Ofcourse, the carrier plate 1042 in some embodiments is configured to becapable of some angular rotation about the longitudinal axis LA1 tofacilitate inducing a skew of the planet axles 1046; however, such anarrangement results only in a slight, operationally irrelevant, angularrotation of the anti-rotation rods 1204 about the longitudinal axis LA1.In one embodiment, in which the carrier plate 1204 is rotatable aboutthe longitudinal axis LA1, the anti-rotation rods 1204 preferably areprovided with an axial degree of freedom relative to the carrier plate1204. Hence, in some embodiments, the anti-rotation rods 1204 areinserted in the shift cam 1200 and the carrier plate 1042 with radialand/or axial clearances to allow relative axial translation between thecarrier plate 1042 and the anti-rotation rods 1204.

The CVT 1004 includes a feedback cam 1206 that couples to planet gears1176 and that is operationally coupled to a skew cam 1208 and to theshift cam 1200. In one embodiment, the feedback cam 1206 and the shiftcam 1200 are coupled through a threaded interface. In some embodiments,the feedback cam 1206 is configured to couple to the skew cam 1208 via abearing 1210 and a skew cam slider 1212. The outer race of the bearing1210 can be press fit, for example, to an inner bore of the feedback cam1206. A clip provided in the inner bore of the feedback cam 1206cooperates with a shoulder of the skew cam slider 1212 to constrainaxially the bearing 1210. In some embodiments, a shoulder (not shown)can be provided on the feedback cam 1206 to axially capture the outerrace of the bearing 1210 between the clip and the shoulder. The skew camslider 1212 is mounted to a main axle 1214 via a sliding splineinterface. The skew cam 1208 is axially constrained in the skew camslider 1212 by, for example, a clip and the bearing 1210. In someembodiments, the skew cam 1208 can be provided with a shoulder thatcontacts the inner race of the bearing 1210.

During a speed ratio adjustment of the CVT 1004, mere rotation of thefeedback cam 1206 causes translation of the shift cams 1200, 1202, butdoes not result in any movement of the skew cam slider 1212 or,consequently, the skew cam 1208. However, translation of the feedbackcam 1206 drives axially the skew cam slider 1212, and thereby the skewcam 1208, via the bearing 1210. Translation of the skew cam 1208 resultsin an angular rotation of the carrier plate 1042 about the longitudinalaxis LA1.

Referencing now FIGS. 33 and 34 specifically, in one embodiment, afeedback cam 1206 is generally a cylindrical, hollow body 1196 having afeedback cam flange 1216 adapted with an inner bore having a toothedportion 1213 configured to couple to planet gears 1176. That is, thefeedback cam flange 1216 is capable of receiving and transmitting arotating force. The feedback cam 1206 includes a threaded portion 1218configured to couple with a corresponding threaded portion 1220 of theshift cam 1200. In some embodiments, the feedback cam 1206 exhibits afeedback cam counterbore 1215 adapted to receive, and facilitate theaxial constraint, of the outer race of the bearing 1210.

Passing now to FIG. 35, in one embodiment, a shift cam 1200 can be agenerally cylindrical body with a threaded inner bore 1220 adapted tomate to the threaded portion 1218 of the feedback cam 1206. The shiftcam 1200 is provided with a profiled surface 1222 for, in someembodiments, guiding the shift cam rollers 1052. In one embodiment, theprofiled surface 1222 is adapted to cooperate with a surface of a leg ofa planet-leg assembly. A bearing race 1224 can be formed into the shiftcam 1200 for receiving bearings that support the traction sun 1026. Inone embodiment, the shift cam 1200 is provided with a shoulder 1223 toreceive the shift cam 1202. In some embodiments, one or more bores 1226are arranged axially around the central bore 1220 to receive and supportthe anti-rotation rods 1204.

Referencing FIG. 36 now, a CVT 1006 can include a first carrier plate1302 and a second carrier plate 1304, both of which are substantiallysimilar to the carrier plates 1040, 1042. The carrier plate 1302 can beconfigured to facilitate the use of a thrust bearing 1306 between thecarrier plate 1302 and an input driver 1308. In one embodiment, thecarrier plate 1302 is rigidly coupled to a planetary carrier 1310, whichis configured to support a set of planetary gears 1312, which areoperationally coupled to a sun gear 1314 and a feedback cam 1316. Thecarrier plate 1302, the planetary carrier 1310, the feedback cam 1316,and the sun gear 1314 are preferably mounted coaxially with thelongitudinal axis LA1. A sun shaft 1318 is placed radially inward of theplanetary carrier 1310, and is operably coupled to the sun gear 1314.

A main axle 1320 is coupled to the planetary carrier 1310, whichplanetary carrier 1310 can be substantially similar to the planetarycarrier 1178 of FIGS. 25 and 26. In some embodiments, the main axle 1320can be provided with an interface 1322 for supporting the feedback cam1316. In one embodiment, the interface 1322 is a sliding bearinginterface, but in other embodiments, the interface 1322 can be aclearance fit between the main axle 1320 and the feedback cam 1316. Asillustrated in FIG. 36, in one embodiment, the main axle 1320 and theplanetary carrier 1310 can be configured to facilitate axial constraintof the sun gear 1314. Hence, the main axle 1320 and/or the carrier 1310can be provided with shoulders or recesses 1315A and 1315B,respectively, that aid in maintaining the axial position of the sun gear1314.

In one embodiment, the main axle 1320 is coupled to a skew cam 1324 via,for example, a sliding spline interface 1326. Hence, the main axle 1320and the skew cam 1324 can be provided with mating sliding splines. Theskew cam 1324 is coupled to the feedback cam 1316 by, for example, athreaded interface 1328. Thus, in some embodiments, the skew cam 1324and the feedback cam 1316 include mating threaded portions. In someembodiments, the skew cam 1324 is coupled to a shift cam anti-rotationretainer 1330 via an anti-rotation coupling 1332, which can be a slidingspline, for example. The shift cam anti-rotation retainer 1330 can becoupled to, or be integral with a shift cam 1334, which is substantiallysimilar to the shift cam of FIG. 6, for example. The shift cam 1334 anda shift cam 1336 are operably coupled to the feedback cam 1316 and to atraction sun 1338 via, respectively, a first thrust bearing 1340 and asecond thrust bearing 1342. The skew cam 1324 is preferably coupled tothe carrier plate 1304 by an interface 1346, which can be a high lead,threaded coupling, in which case the skew cam 1324 and the carrier plate1304 can be provided with mating high lead threads.

In one embodiment, the main axle 1320 can be fixed to ground by theplanetary carrier 1310 and a carrier plate retainer 1344. Hence, themain axle 1320, the planetary carrier 130, and the carrier plateretainer 1344 are fixed axially, rotationally, and radially relative tothe longitudinal axis LA1. Consequently, the skew cam 1324, theanti-rotation retainer 1330 and the shift cams 1334, 1336 are configuredto be non-rotatable about the longitudinal axis LA1. In someembodiments, the anti-rotation retainer 1330 is provided with anextension (shown but no labeled) adapted to butt up against the carrierplate 1304, and thus, provide a limit stop when shifting the CVT 1006.In one embodiment, the carrier plate retainer 1344 threads to the mainaxle 1320 via a threaded interface 1348. The carrier plate retainer 1344can be adapted to receive a carrier retaining bolt 1350 that isconfigured to cooperate with the carrier plate retainer 1344 toconstrain axially the carrier plate 1304. In some such embodiments, thecarrier plate 1304 can be provided with a carrier slot 1352 that allowsthe carrier plate 1304 to rotate angularly about the longitudinal axisLA1 in a plane perpendicular to said axis. Of course, it is preferableto ensure that the interfaces between the carrier plate 1304, thecarrier plate retainer 1344, and the carrier retaining bolt 1350minimize friction while allowing the carrier plate 1304 to rotaterelative to the carrier plate retainer 1344 and the carrier retainingbolt 1350. In one embodiment, the carrier plate 1304 and/or the carrierplate retainer 1344 are provided with, for example, shoulders and/orrecesses to provide radial support for the carrier plate 1304.

To adjust the speed ratio of the CVT 1006, a rotation of the sun shaft1318 causes a rotation of the feedback cam 1316 via the sun gear 1314and the planetary gears 1312. As previously discussed with reference toFIGS. 6 and 24, rotation of the feedback cam 1316 causes a translationof the feedback cam 1316, when the skew cam 1324 does not translate, orcauses a translation of both the feedback cam 1316 and the skew cam1324, when the shift cams 1334, 1336 and the traction sun 1338 are underclamp loads. Through the interface 1346, translation of the skew cam1324 imparts an angular rotation of the carrier plate 1304; therebyinducing the CVT 1006 into a skew condition, or conversely, restoringthe carrier plate 1304 to a different or zero skew condition. Asexplained above, the inducement of a skew condition can result in anadjustment of the speed ratio of a CVT.

In one embodiment, the CVT 1006 can be provided with a side forceneutralizer mechanism. In the embodiment of FIG. 36, a side forceneutralizer can include a first resistance member 1354 mounted coaxiallyabout the longitudinal axis LA1. The first resistance member 1354 canbe, for example, one or more springs. In some embodiments, the firstresistance member 1354 is arranged about the longitudinal axis LA1, butis not necessarily concentric with the longitudinal axis LA1. A firstreaction ring 1356 is placed adjacent to the first resistance member1354, and is mounted coaxially about the longitudinal axis LA1. A clipor shim 1358 is configured to provide an axial constraint for the firstreaction ring 1356. Hence, the first reaction ring 1356 is movableaxially against the first resistance member 1354, but the first reactionring 1356 cannot move axially past the shim 1358. In one embodiment, theshim 1358 is aligned axially and radially by the carrier plate retainer1344 and the main axle 1320. As shown, in some embodiments, the firstresistance member 1354, the first reaction ring 1356, and the shim 1358are housed, at least partially, by one or both of the main axle 1320 andthe carrier plate retainer 1344.

The main axle 1320 can be adapted to receive and support a pin carrier1360 that is configured to receive and support a skew cam pin 1362. Thepin carrier 1360 has a first end that engages the first reaction ring1356 and a second end that engages a second reaction ring 1364. The pincarrier 1360 is provided with a substantially lateral bore configured toreceive and support the skew cam pin 1362 by, for example, a press fit.The pin carrier 1360 is configured to mate with the main axle 1320either by a clearance fit or through a sliding fit, for example. Themain axle 1320 can be provided with a slot 1361 for facilitating thecoupling of the skew cam pin 1362 to the skew cam 1324. The skew cam pin1362 can facilitate an axial translation of the skew cam 1324. As shownin FIG. 36, the main axle 1320 can be provided with a retaining stop1366 configured to prevent axial translation of the second reaction ring1364 in one direction. Adjacent to the second reaction ring 1364, incontact therewith, and mounted coaxially (in some embodiments) about thelongitudinal axis LA1, there can be a second resistance member 1368,which can be one or more springs. In one embodiment, a spacer 1370 canbe positioned between the second resistance member 1368 and a preloadadjuster 1372. The spacer 1370 primarily provides a coupling between thesecond resistance member 1368 and the preload adjuster 1372. In someembodiments, the preload adjuster 1372 can be a set screw, for example.The pin carrier 1360, the second reaction ring 1364, the secondresistance member 1368, the spacer 1370, and the preload adjuster 1372are mounted coaxially about the longitudinal axis LA1 and are axiallymovable; however, the axial movement of the first and second reactionrings 1356, 1364 is limited by, respectively, the shim 1358 and theretaining stop 1366.

The first resistance member 1354, the second resistance member 1368, thespacer 1370, and the set screw 1372 are preferably selected to provide asuitable preload and/or desired resistance response characteristic forovercoming the tendency of the side force to act upon the skew cam 1324and induce a non-zero skew condition. During operation, an axialtranslation of the skew cam 1324 will tend to be resisted by the firstand the second resistance members 1354, 1368. As the skew cam 1324translates leftward (on the orientation of the page), the skew cam 1324acts upon the skew cam pin 1362. This action translates the pin carrier1360 axially, which engages the first reaction ring 1356. The firstresistance member 1354 resists translation of the first reaction ring1356. As the skew cam 1324 translates rightward, in a similar fashion,the skew cam 1234 operably engages the second reaction ring 1368, whichis resisted by the second resistance member 1368. It should be notedthat the action of the first and second resistance members 1354, 1368 isdecoupled (that is, independent of one another) through the axialconstraints provided by the shim 1358 and the retaining stop 1366.

To recap some of the disclosure above, in one embodiment, the main axle1320 includes at least some of the following aspects. The central boreis adapted to receive the pin carrier 1360. The central bore can exhibitthe retaining stop 1366, as well as, the threaded portion for receivingthe preload adjuster 1372. The main axle 1320 preferably includes theslot 1361 adapted to allow passage of the skew cam pin 1362 from insidethe main axle 1320 to an exterior space of the main axle 1320. Anexterior diameter of the main axle 1320 can include the first threadedinterface 1348 for rigidly coupling to a grounded member, such as thecarrier plate retainer 1344. The exterior diameter of the main axle 1320can further include a sliding spline portion for engaging a matingsliding spline of the skew cam 1324. The skew cam 1324 can be a tubularbody having an inner diameter and an outer diameter. The inner diameterof the skew cam 1324 can be provided with a recess (shown but notlabeled) for receiving the skew cam pin 1362. The inner diameter of theskew cam 1324 can include a splined portion for engaging correspondingsplines of the main axle 1320. A portion of the exterior diameter of theskew cam 1324 can be provided with a high lead threaded portion forengaging a mating threaded portion of the carrier plate 1304. The skewcam 1324 can include a threaded portion, of relatively low lead whencompared to the high lead portion, for engaging a similarly threadedportion of the feedback cam 1316. In some embodiments, the skew cam 1324is adapted with a sliding spline portion on its outer diameter to engagea corresponding sliding spline of the anti-rotation retainer 1330.

Turning to FIGS. 37 and 38 now, a CVT 1008 is similar to the CVT 1006 inmany respects. However, the CVT 1008 is provided with an alternativeside force neutralizer. Those components of the CVT 1008 that aresubstantially similar to components of the CVT 1006 will not bespecifically addressed in detail in the following discussion. The CVT1008 includes the first carrier plate 1302 that is rigidly coupled tothe planetary carrier 1310. An input driver 1308 can be supported by,and reacted by, the first carrier plate 1302 through a bearing 1306. Aplanetary reference input 1410 can be coupled to a feedback cam 1316.The planetary reference input 1410 can be as previously described withreference to FIGS. 24 and 36, for example. A skew cam 1325 couples,similarly as previously described with reference to FIG. 36, to thefeedback cam 1316, the anti-rotation retainer 1330, and the carrierplate 1304. The skew cam 1325 can also couple to a main axle 1404 in asubstantially similar manner as the skew cam 1324 of FIG. 36 couples tothe main axle 1320.

Referencing FIG. 38 more specifically, the CVT 1008 can be provided witha side force neutralizer that includes a first resistance member 1355mounted coaxially with the longitudinal axial LA1 and the main axle1404. A flange 1402 of the main axle 1404 is rigidly coupled to a flangeextension 1406, which is rigidly coupled to a shoulder stop 1408. Atranslating cup 1412 mounts coaxially with the main axle 1404 and isplaced radially inward of the flange extension 1406. In one embodiment,the translating cup 1412 contacts the flange 1402 and has a clearancefit relative to the flange extension 1406. In some embodiments, atranslating cup cap 1414 can be rigidly coupled to the translating cup1412, thereby forming a holding space for the first resistance member1355. The skew cam 1325 can be provided with a catch 1416 adapted toengage the translating cup 1412. In some embodiments, the firstresistance member 1355 is positioned between the catch 1416 and thetranslating cup cap 1414 or the flange 1402. A second resistance member1369 can be mounted coaxially about the main axle 1404 and can bepositioned between the translating cup 1412 and the shoulder stop 1408.

In operation, axial translation of the skew cam 1325 toward the carrierplate 1302 is resisted by the first resistance member 1355, as the firstresistance member 1355 is reacted by the translating cup cap 1414 and/orthe flange 1402. It should be recalled that the main axle 1404 can befixed to ground; hence, the main axle 1404 can be configured to nottranslate axially. As the skew cam 1325 translates axially toward thecarrier plate 1304, the second resistance member 1369 tends to resistthis axial movement of the skew cam 1324A, since the second resistancemember 1369 is supported by the shoulder stop 1408, which is rigidlycoupled to the main axle 1404 through the flange extension 1406. Theresistance members 1355, 1369 are preferably selected to provide desiredcharacteristics in overcoming the effects of the side force upon theskew cam 1325. It should be noted that in some embodiments the interfacebetween the feedback cam 1316 and the flange extension 1406, as well asthe interface between the translating cup 1412 and the flange extension1406, are suitably configured to minimize sliding friction.

Passing to FIGS. 39 and 40 now, a CVT 1009 is substantially similar invarious respects to the CVTs 1006 and 1008. In one embodiment, a skewcam 1502 couples rigidly to an extension sleeve 1504 of a neutralizer1506, which is generally shown in Detail F. In some embodiments, theneutralizer 1506 includes a resistance member locator 1508 that isadapted to receive the first and second resistance members 1357, 1371.The resistance member locator 1508 is preferably rigidly coupled to amain axle 1510, and is mounted coaxially therewith. In one embodiment,the first resistance member 1357 is mounted coaxially with the main axle1510, and is located axially between a flange 1402 of the main axle 1510and a first resistance ring or a shim 1512. The first resistance member1357 and the first resistance ring 1512 are received in a recess formedby the main axle 1510 and a stop shoulder 1514 of the resistance memberlocator 1508. The second resistance member 1371 can be located axiallybetween a stop cap 1516 of the resistance member locator 1508 and asecond resistance ring or shim 1518. In some embodiments, the secondresistance member 1371 and the second resistance ring 1518 are mountedcoaxially with the main axle 1510. A catch flange 1520 of the extensionsleeve 1504 is positioned between the first and second resistance rings1512, 1518. The stop shoulder 1514 is suitably configured to provide anaxial stop for the first and second resistance rings 1512, 1518 in atleast one axial direction. The stop shoulder 1514 constrains axialtranslation of the first resistance ring 1512 in a first direction, andthe stop shoulder 1514 constrains axial translation of the secondresistance ring 1518 in second direction.

During operation, as the skew cam 1502 translates towards the carrierplate 1302, the first resistance member 1357 tends to oppose thetranslation of the skew cam 1502 through the operational couplingbetween the skew cam 1502 and the first resistance member 1357 via thefirst resistance ring 1512, the catch flange 1520, and the extensionsleeve 1504. Similarly, as the skew cam 1502 translates toward thecarrier plate 1304, the second resistance member 1371 tends to opposethe translation of the skew cam 1502 through the operational couplingbetween the skew cam 1502 and the second resistance member 1371 via thesecond resistance ring 1518, the catch flange 1520, and the extensionsleeve 1504. It should be noted that as the catch flange 1520 acts uponeither one of the first and second resistance rings 1512, 1518, theother one of the first and second resistance members 1357, 1371 is notengaged or energized. Hence, the actions of the first and secondresistance members 1357, 1371 are decoupled. Preferably, the first andsecond resistance members 1357, 1371 are suitably selected to providethe desired response characteristics to move the skew cam 1502 to aposition corresponding to a CVT skew condition of nominal zero skewangle.

It should be noted that the neutralizer 1506 need not employ all of thecomponents described above. For example, in some embodiments, the firstresistance member 1357 and the first resistance ring 1512 can beprovided as a suitable configured single piece component that performsthe desired resistance function as it engages the catch flange 1520. Asshown best in FIG. 39, in some embodiments, the neutralizer 1506 ishoused at least partially in a bore of the feedback cam 1316.

Referring now to FIGS. 41-45, a CVT 4100 can be configured in variousrespects similarly to the CVT 1000 and the CVT 1002. In someembodiments, the CVT 4100 includes a control reference assembly 4300,which will now be discussed. In one embodiment, a control reference nut4302 is coaxially located with a main shaft 4135 and is coupled to anintermediate reaction member 4304. Spring members 4306 and 4308 providebidirectional spring support between the control reference nut 4302 andthe intermediate reaction member 4304. An adjustment in one direction ofthe control reference nut 4302 tends to energize torsionally the springmember 4306 and an adjustment in the other direction tends to energizetorsionally the spring member 4308. Once energized, the spring member4306 or 4308 exerts a force on the intermediate reaction member 4304 andthereby exerts force onto a feedback cam 4102 until an adjustment intilt angle is achieved. Some operating conditions of CVT 4100 generateforces that tend to resist the adjustment of the feedback cam 4102, andconsequently, those forces also resist adjustment of the controlreference nut 4302. The feedback cam 4102 is substantially similar tothe feedback cam 1206. In some embodiments, it is preferable to minimizethe, or limit the maximum, effort required to adjust the controlreference nut 4302. In the embodiment shown in FIG. 41, the controlreference assembly 4300 facilitates the adjustment of the controlreference nut 4302 even in the presence of high resistance on thefeedback cam 4102.

In one embodiment of the control reference assembly 4300, the springmembers 4306 and 4308 are torsion springs formed with legs 4322, 4324and 4326, 4328, respectively, that are operationally connected to thecontrol reference nut 4302 and the intermediate reaction member 4304.The leg 4322 is rotatably constrained in one direction by a shoulder4320 on the control reference nut 4302. The leg 4324 is rotatablyconstrained in two directions by a bore 4330 formed on the intermediatereaction member 4304. Similarly, the leg 4328 is constrained by ashoulder 4315 in one direction, and the leg 4326 is constrained in twodirections by a bore 4332 (see FIG. 45) formed on the intermediatereaction member 4304.

Referencing FIG. 44 more specifically now, in one embodiment the controlreference nut 4302 is a generally cylindrical body with an outer ring4312 adapted to couple to an adjustment interface (not shown) such as acable pulley or other actuator. First and second recesses 4316 and 4318are formed on the inner diameter of the control reference nut 4302 toreceive and retain, for example, the torsion spring 4308. Similarly,first and second recesses 4317 and 4319 are adapted to receive andretain the torsion spring 4306. In one embodiment, the recess 4318 isformed on substantially half of the perimeter of the inner diameter, andon a first end, of the control reference nut 4302. The recess 4318facilitates the retention of the leg 4322 in one direction and providesclearance for the leg 4322 in the opposite direction. The recess 4317 isformed on a second end of the inner diameter of the control referencenut 4302. The recesses 4317 and 4318 provide a degree of freedom to thelegs 4322 and 4328 that facilitates the energizing of one spring member4306, 4308 while the other spring member 4306, 4308 is allowed to rotatewithout being energized.

Passing now to FIGS. 42 and 45, in one embodiment the intermediatereaction member 4304 can be a generally cylindrical body having asplined inner bore 4310 that mates, for example, to the feedback cam4102. A first and a second retention bore 4330 and 4332 can be formed onthe outer diameter of the intermediate reaction member 4304. Theretention bores 4330, 4332 can receive the legs 4324 and 4326. Toaxially retain the spring members 4306 and 4308, respective first andsecond shoulders 4334 and 4335 are, in some embodiments, coupled to theouter diameter of the intermediate reaction member 4304.

In one embodiment, the CVT 4100 can be provided with a side forceneutralizer assembly 4192, an embodiment of which is generally shown inDetail G view of FIGS. 41 and 47. In some embodiments, the neutralizer4192 includes a first resistance member 4194 positioned between an axialresistance plate 4184 and a translating resistance cup 4196. The axialresistance plate 4184 is rigidly coupled to a main shaft 4135. The firstresistance member 4194 and the translating resistance cup 4196 aremounted adjacent to one another and coaxially about the longitudinalaxis LA1. A neutralizer reaction flange 4198 can be coupled to a skewcam 4168. The neutralizer reaction flange 4198 is positioned adjacent tothe translating resistance cup 4196. A second resistance member 4195 ispositioned between the neutralizer reaction flange 4198 and aneutralizer stop cap 4105 that can be rigidly mounted to the translatingresistance cup 4196, all of which are mounted coaxially about thelongitudinal axis LA1. The neutralizer stop cap 4105 is axiallyconstrained by, for example, a neutralizer retainer plate 4103 that ispreferably rigidly coupled to the axial retainer plate 4184 and providedwith a sliding interface 4104.

Passing now to FIGS. 48-50, in one embodiment a CVT 4600 can beconfigured in various respects substantially similar to the CVT 1000.The CVT 4600 can be provided with a control reference assembly 4602. Inthe embodiment shown, the control reference assembly 4602 can include acontrol reference nut 4708 coaxially arranged about the main shaft 4601that is coupled to a pulley 4702 by cables 4704 and 4706. The pulley4702 is coupled to a spring retention member 4710 at an interface 4711.In some embodiments, the interface 4711 can be a splined interface andin other embodiments the interface 4711 can be a press fit between thepulley 4702 and the spring retention member 4710. The spring retentionmember 4710 is coupled to a spring reaction member 4712 in a similarmanner as the control reference nut 4302 is coupled to the intermediatereaction member 4304 described with reference to FIGS. 41-46. One end ofthe cable 4706 is retained in the control reference nut 4708 at a bore4804B, while another end of the cable 4706 is retained at a bore 4806Bformed in the pulley 4702; the cable 4706 can be coupled to the bores4804B, 4806B in a suitable manner, such as with a set screw or with anadhesive. Similarly, one end of the cable 4704 is retained in thecontrol reference nut 4708 at a bore 4804A, while another end of thecable 4704 is retained at a bore 4806A formed in the pulley 4702. Thecables 4704 and 4706 are wrapped around the pulley 4702 in a set ofhelical grooves 4810A and 4810B.

Referring now to FIGS. 51A-56, in one embodiment, a CVT 5100 can beconfigured to be similar in various respects to the previously describedCVTs; therefore, only certain differences between the previousembodiments and the CVT 5100 will be described. The CVT 5100 can includea first carrier plate 5101 and a second carrier plate 5102 that can becoupled together with a number of carrier rods 5103. The carrier plates5101, 5102 each can have a number of radial slots 5104. In oneembodiment, the CVT 5100 includes a number of traction planets 5106arranged angularly about a main axle 5108. The main axle 5108 generallydefines a longitudinal axis of the CVT 5100. Each of the tractionplanets 5106 is configured to rotate about a planet axle 5110. Theplanet support trunnion is configured to receive and support each end ofthe planet axle 5110.

In one embodiment, the planet support trunnion 5112 is a generallyu-shaped body (FIG. 56) having a central bore 5114 and first and secondlegs 5116A, 5116B extending from the central bore 5114. A slot 5117 canbe provided on the u-shaped body and arranged to bisect at least aportion of the legs 5116A, 5116B. The first leg 5116A can be providedwith an eccentric skew cam 5118A. The second leg 5116B can be providedwith an eccentric skew cam 5118B. The eccentric skew cams 5118A and5118B are adapted to couple to the radial slot 5104. The planet supporttrunnion 5112 can have bores 5119 adapted to couple to, and providesupport for, the planet axle 5110. In one embodiment, the bores 5119have a center axis 51190. The eccentric skew cams 5118A and 5118B can beprovided with center axes 51180A and 51880B, respectively. The centeraxis 51190 and the center axes 51180A, 5118B can be configured to benon-concentric. In some embodiments, the eccentric skew cams 5118A,5118B can have curved profiles around the circumference. In otherembodiments, the eccentric skew cams 5118A, 5118B can have circularprofiles. In one embodiment, the center axis 51180A is radially outward(with respect to a central, longitudinal axis of the CVT 5100) of thecenter axis 51190, while the center axis 51180B is radially inward ofthe center axis 51190 (see, for example, FIGS. 53A and 53B).

In one embodiment, the CVT 5100 is provided with traction sun 5120 thatcan be configured to rotate about the main axle 5108. The traction sun5120 is positioned radially inward of, and in contact with, each of thetraction planets 5106. In some embodiments, the traction sun 5120 isoperably coupled to the first and the second carrier plates 5101 and5102 via bearings, for example, that can be axially positioned by anumber of bearing support fingers 5124 (see FIG. 54) coupled to thecarrier plates 5101 and 5102.

Referring again to FIG. 52, in one embodiment, the CVT 5100 can beprovided with a shift rod 5126 that is mounted coaxial about the mainaxle 5108. In some embodiments, the shift rod 5126 slidingly couples tothe main axle 5108, while in other embodiments, the shift rod 5126 isoperably coupled to the main axle 5108 via bearings (not shown). Theshift rod 5126 can be provided with a threaded portion 5128 that isadapted to couple to a sleeve 5130. The sleeve 5130 operably couples tothe planet support trunnion 5112 via a pin 5132.

Referring to FIG. 55, in one embodiment, the sleeve 5130 is providedwith a threaded inner bore 5134. A number of reaction shoulders 5136 canbe arranged angularly about, and extend radially from, the threadedinner bore 5134. The reaction shoulders can be configured to be receivedin the slot 5117 of each of the planet support trunnions 5112. In someembodiments, each reaction shoulder 5136 is provided with a slot 5138that is adapted to couple to the pin 5132.

During operation of CVT 5100, a change in the speed ratio of the CVT5100 can be achieved by tilting the planet axles 5110. The planet axles5110 can be tilted by pivoting the planet support trunnions 5112. Theplanet support trunnions 5112 can be pivoted using any suitable method.One method for pivoting the planet support trunnion 5112 involvesrotating the shift rod 5126 and, thereby, axially translating the sleeve5130 and the pin 5132. A second method for pivoting the planet supporttrunnions 5112 involves rotating the shift rod 5126 thereby rotating thesleeve 5130. A rotation of the sleeve 5130 engages the reactionshoulders 5136 with the planet support trunnions 5112. The reactionshoulders 5136 urge the planet support trunnions 5112 to rotate aboutthe skew cam center axes 51180A and 51180B, which moves the center axis51190. The movement of the center axis 51190 induces a skew angle on theplanet axle 5119. The skew angle, as discussed previously, motivates achange in the tilt angle of the planet axle 5110. Under some operatingconditions, for example under a high torque condition, the second methodmay be preferred.

Passing now to FIGS. 57-58, in one embodiment, a torque governor 5700can be adapted to cooperate with embodiments of CVTs previouslydisclosed such as CVT 4100 or 5100, for example. For descriptionpurposes, the torque governor 5700 includes a representative carrierplate 5702 that can be substantially similar to the carrier plates 1302,4604, or 5102, for example. The torque governor 5700 can include atraction sun 5704 that is substantially similar to the traction sun 310,for example. The torque governor 5700 can also include a shift cam 5706that is substantially similar to the shift cam 1200, for example. In oneembodiment, the torque governor 5700 includes first and second reactionarms 5710 and 5712, both of which can be operably coupled to the carrierplate 5702 via springs 5714. The torque governor 5700 can also include apreload adjuster 5716 coupled to the first and the second reaction arms5710 and 5712. In one embodiment, the preload adjuster 5716 has threadedends and can be configured to operate as a common turn-buckle, or othersimilar device, for positioning the reaction arms 5710 and 5712. Thereaction arms 5710 and 5712 can be configured in a scissor-likearrangement.

In one embodiment, the shift cam 5706 and the carrier plate 5702 can beadapted to couple to traction planet assemblies 1044 (not shown in FIGS.57-58), for example, in a substantially similar manner as previouslydescribed for embodiments of continuously variable transmission adaptedwith various inventive skew-based control systems. In one embodiment,the shift cam 5706 includes a threaded extension 5707 that is configuredto operably couple to a central bore of the carrier plate 5702. A spring5720 can be operably coupled to the carrier plate 5702 and the shift cam5706. The threaded extension 5707 can couple to a mating threaded boreof the reaction arm 5710.

During operation, the torque governor 5700 can adjust the transmissionspeed ratio to maintain a constant operating torque. An axialtranslation of the traction sun 5704 due to a change in operating torquecauses an axial translation of the shift cam 5706 and the threadedextension 5707. The threaded extension 5707 engages the first reactionarm 5710 and converts the axial translation into a rotation of the firstreaction arm 5710. The rotation of the first reaction arm 5710 energizesthe spring 5714A and urges the carrier plate 5702 to rotate. It shouldbe readily apparent that the spring 5714B can be energized by the secondreaction arm 5712 under an operating condition that causes an axialtranslation of the threaded extension 5707 in an opposite direction thanthe one described here as an illustrative example. The rotation of thecarrier plate 5702 induces a skew angle on the traction planetassemblies 1044. As previously discussed, the skew angle motivates ashift in the transmission 5700. As the transmission shifts, the tractionsun 5704 axially displaces and the carrier plate 5702 returns to anequilibrium position. Since the first reaction arm 5710 is operablycoupled to the second reaction arm 5712 via springs 5714, theequilibrium condition can be set with the preload adjuster 5716 that isrepresentative of a desired operating torque.

It should be noted that the description above has provided dimensionsfor certain components or subassemblies. The mentioned dimensions, orranges of dimensions, are provided in order to comply as best aspossible with certain legal requirements, such as best mode. However,the scope of the inventions described herein are to be determined solelyby the language of the claims, and consequently, none of the mentioneddimensions is to be considered limiting on the inventive embodiments,except in so far as anyone claim makes a specified dimension, or rangeof thereof, a feature of the claim.

The foregoing description details certain embodiments of the invention.It will be appreciated, however, that no matter how detailed theforegoing appears in text, the invention can be practiced in many ways.As is also stated above, it should be noted that the use of particularterminology when describing certain features or aspects of the inventionshould not be taken to imply that the terminology is being re-definedherein to be restricted to including any specific characteristics of thefeatures or aspects of the invention with which that terminology isassociated.

What we claim is:
 1. A method of controlling a continuously variabletransmission (CVT) having a plurality of traction planets with tiltableaxles of rotation, the method comprising the steps of: providing acontrol reference indicative of a desired operating condition of theCVT; sensing a current operating condition of the CVT; comparing thedesired operating condition with the current operating condition therebygenerating a control error; and imparting a skew angle to each of thetiltable axles, the skew angle based at least in part on the controlerror, wherein sensing a current operating condition comprises providingan axial position of a traction sun, said axial position beingindicative of the current operating condition of the CVT.
 2. The methodof claim 1, wherein imparting a skew angle comprises imparting a carrierplate angle to a carrier plate of the CVT.
 3. The method of claim 2,wherein imparting a carrier plate angle comprises applying a gain to thecontrol error.
 4. The method of claim 1, further comprising the step oftilting the planet axles, wherein the rate of change in the tilt angleof the planet axles is based at least in part on the skew angle.
 5. Themethod of claim 4, wherein the tilting of the planet axles comprisesproviding an integrator means configured to convert the rate of changein the tilt angle into a tilt angle of the planet axles.
 6. The methodof claim 5, wherein imparting a skew angle comprises providing afunction configured to determine a skew angle based at least in part ona carrier plate angle of the CVT.
 7. The method of claim 1, furthercomprising adjusting a speed ratio of the CVT based at least in part onthe skew angle.
 8. The method of claim 1, wherein sensing a currentoperating condition comprises determining the magnitude of an axialforce exerted on a traction sun, wherein the magnitude of the force isindicative of the current operating condition of the CVT.
 9. The methodof claim 8, wherein sensing the current operating condition comprisessensing a force imparted on a carrier plate of the CVT.
 10. The methodof claim 9, wherein sensing the current operating condition comprisessensing a force imparted on the control reference.
 11. The method ofclaim 10, wherein sensing the current operating condition comprisessumming at least the axial force, the force imparted on the carrierplate, and the force imparted on the control reference.
 12. The methodof claim 11, wherein sensing the current operating condition comprisesproviding first and second integrators coupled to the said summation.13. The method of claim 8, wherein providing a control referencecomprises providing a reference speed ratio and a reference torque. 14.A method of controlling a continuously variable transmission (CVT)having a plurality of traction planets with tiltable axles of rotation,the method comprising the steps of: providing a control referenceindicative of a desired operating condition of the CVT; sensing acurrent operating condition of the CVT; comparing the desired operatingcondition with the current operating condition thereby generating acontrol error; and imparting a skew angle to each of the tiltable axles,the skew angle based at least in part on the control error, whereinimparting a skew angle comprises imparting a carrier plate angle to acarrier plate of the CVT.
 15. The method of claim 14, wherein impartinga carrier plate angle comprises applying a gain to the control error.16. The method of claim 14, further comprising the step of tilting theplanet axles, wherein the rate of change in the tilt angle of the planetaxles is based at least in part on the skew angle.
 17. A method ofcontrolling a continuously variable transmission (CVT) having aplurality of traction planets with tiltable axles of rotation, themethod comprising the steps of: providing a control reference indicativeof a desired operating condition of the CVT; sensing a current operatingcondition of the CVT; comparing the desired operating condition with thecurrent operating condition thereby generating a control error; andimparting a skew angle to each of the tiltable axles, the skew anglebased at least in part on the control error, wherein sensing a currentoperating condition comprises determining the magnitude of an axialforce exerted on a traction sun, wherein the magnitude of the force isindicative of the current operating condition of the CVT.
 18. The methodof claim 17, wherein sensing the current operating condition furthercomprises sensing a force imparted on a carrier plate of the CVT. 19.The method of claim 18, wherein sensing the current operating conditionfurther comprises: sensing a force imparted on the control reference;and summing at least the axial force, the force imparted on the carrierplate, and the force imparted on the control reference.
 20. The methodof claim 17, wherein providing a control reference comprises providing areference speed ratio and a reference torque.